BP-Social Theme headers error when attempting to log in - can't access dashboard

Greetings,
I am using the bp-social theme along with a members plugin. I haven't logged in to the site in several months and when I tried to get in today I receive a long list of header errors (see below) and am unable to access the dashboard. However, the website appears and functions fine (www.pagosarotary.org/morning).

When I attempt to login using /wp-admin (rather then the login widget on the main site), I receive a header error referring to line 881. No login box appears.

Without being able to access the dashboard, I am unable to see if there is an outdated plugin that is causing the problem. Is there a way to deactivate plugins via code, without using the Wordpress dashboard?

Thank you for your help!
-natalie

PAGE ERRORS THAT APPEAR AFTER CLICKING THE LOGIN BUTTON:
(http://pagosarotary.org/morning/wp-login.php)

Warning: Cannot modify header information - headers already sent by (output started at /home/content/...ng/wp-content/themes/bp-social/functions.php:1) in /home/content/p/a/g/pagosascene/html/pagosarotary/morning/wp-login.php on line 362

Warning: Cannot modify header information - headers already sent by (output started at /home/content/.../wp-content/themes/bp-social/functions.php:1) in /home/content/p/a/g/pagosascene/html/pagosarotary/morning/wp-login.php on line 374

Warning: Cannot modify header information - headers already sent by (output started at /home/content/.../wp-content/themes/bp-social/functions.php:1) in /home/content/p/a/g/pagosascene/html/pagosarotary/morning/wp-includes/pluggable.php on line 680

Warning: Cannot modify header information - headers already sent by (output started at /home/content/.../wp-content/themes/bp-social/functions.php:1) in /home/content/p/a/g/pagosascene/html/pagosarotary/morning/wp-includes/pluggable.php on line 681

Warning: Cannot modify header information - headers already sent by (output started at /home/content/.../wp-content/themes/bp-social/functions.php:1) in /home/content/p/a/g/pagosascene/html/pagosarotary/morning/wp-includes/pluggable.php on line 682

Warning: Cannot modify header information - headers already sent by (output started at /home/content/.../wp-content/themes/bp-social/functions.php:1) in /home/content/p/a/g/pagosascene/html/pagosarotary/morning/wp-includes/pluggable.php on line 881