Memory issue

I’m seeing this error on my dashboard:

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 3789528 bytes) in /home/eyamane/public_html/wp-includes/class-feed.php on line 4

I have my memory bumped up to 256M in wp-config:

define(‘WP_MEMORY_LIMIT’, ‘256M’);

I do not have access to php.ini, so this is the only place I have modified. I tried adding to .htaccess:

php_value memory_limit 256M

But this caused internal server error. Is there something else I need to modify other than the wp-config?