ERROR: Cookies are blocked due to unexpected output.

I’m the webmaster of my temple’s website and recently the person doing the content informed me that he has trouble logging in. On the wp-login.php page, there is a message above the login fields stating this:

ERROR: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums.

The homepage of the website is showing blank white at https://kinrarametta.org/en/

I have disabled plugins via phpmyadmin by changing the active_plugins row in wp_options table to a:0:{}.
I also deleted my site’s theme (vantam church-event) so that it will default to twentyfifteen or twentysixteen.

My WordPress was automatically upgraded to v4.4.1 in the last few days although this problem had been around since couple weeks back when it was on v4.2.4.

I have followed some of the forum posts suggesting to change the encoding of wp-config.php and other problematic files from error_log to UTF-8 and not UTF-8 BOM. However, this problem still persists.

Here are the last few items from the error_log file

[10-Jan-2016 08:09:25 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 08:52:09 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 10:01:37 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 10:01:37 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 10:11:11 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 10:11:11 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 10:11:13 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 10:11:35 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 10:11:35 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 10:42:49 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 10:58:10 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 11:11:08 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 12:29:53 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-content/plugins/the-events-calendar/src/Tribe/iCal.php on line 328
[10-Jan-2016 12:29:53 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-content/plugins/the-events-calendar/src/Tribe/iCal.php on line 329
[10-Jan-2016 12:44:21 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-content/plugins/the-events-calendar/src/Tribe/iCal.php on line 328
[10-Jan-2016 12:44:21 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-content/plugins/the-events-calendar/src/Tribe/iCal.php on line 329
[10-Jan-2016 13:35:10 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228
[10-Jan-2016 13:59:41 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 13:59:41 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 13:59:44 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 13:59:44 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 14:00:16 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 14:00:16 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 14:00:23 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 14:00:23 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 14:00:23 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 955
[10-Jan-2016 14:00:23 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 956
[10-Jan-2016 14:00:23 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 957
[10-Jan-2016 14:08:08 UTC] PHP Fatal error:  Call to undefined function wpv_get_option() in /home/kinraram/public_html/en/wp-content/plugins/vamtam-push-menu/push-menu.php on line 125
[10-Jan-2016 14:08:09 UTC] PHP Fatal error:  Call to undefined function wpv_get_option() in /home/kinraram/public_html/en/wp-content/plugins/vamtam-push-menu/push-menu.php on line 125
[10-Jan-2016 14:08:10 UTC] PHP Fatal error:  Call to undefined function wpv_get_option() in /home/kinraram/public_html/en/wp-content/plugins/vamtam-push-menu/push-menu.php on line 125
[10-Jan-2016 14:08:10 UTC] PHP Fatal error:  Call to undefined function wpv_get_option() in /home/kinraram/public_html/en/wp-content/plugins/vamtam-push-menu/push-menu.php on line 125
[10-Jan-2016 14:08:12 UTC] PHP Fatal error:  Call to undefined function wpv_get_option() in /home/kinraram/public_html/en/wp-content/plugins/vamtam-push-menu/push-menu.php on line 125
[10-Jan-2016 14:17:40 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 14:17:40 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 14:17:43 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 14:17:43 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 14:17:45 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 387
[10-Jan-2016 14:17:45 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-login.php on line 400
[10-Jan-2016 14:18:53 UTC] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/kinraram/public_html/en/wp-includes/rest-api.php:1) in /home/kinraram/public_html/en/wp-includes/pluggable.php on line 1228

I’m not sure how I can resolve this issue already. Anyone who can help with any suggestions on what I can try will be greatly appreciated! Thank you very much.