Facebook login became unusually/unusably slow (all of a sudden)

Hi,
First off : thanks for your work on this plugin.
Has been working good up till now.

When I try to login through Facebook the process becomes unbareably slow. (and it didn’t used to be like that).

As I’m still developing the site, surely I have added a lot of stuff, but I’m not sure if/that I added stuff that would mess up the login procedure.

I’ve checked with Chrome dev tools and noticed that the process is “hanging” on my wp-login.php page … (takes 16 seconds) …

When I login “normally” , with my WordPress username/password combo it’s as fast as ever.
Just through the Facebook login , it becomes slow again.

I’ve added a screenshot of the “firebug” status of the page that is causing the slowness:
screenshot here

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edit : done some more research.
This page : https://www.mysite.com/site/wp-content/plugins/wordpress-social-login/services/authenticate.php?provider=Facebook

is taking 10seconds (almost consistently) to pass through …

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edit 2: did a fresh WP install on the same server – installed WordPress Social login and have the exact same issue…. takes 10 or more secs to authenticate through FB.
I’m starting to suspect this is a server issue. (altho it worked fine before)