504 Gateway Time-out: Custom Sidebars and/or Membership 2

I am getting the following error on my site when either of these two plugins are installed and I log into the WordPress back end.

Error:

504 Gateway Time-out
Gateway Time-out The gateway did not receive a timely response from the upstream server or application.

I have already reached out to my hosting company (Dreamhost) who recommended me to turn off all my plugins and reactivate them one by one till I found the one causing the error. Then they recommended me to contact the developer of the plugin.

I have moved both these plugins to an "OFF" folder within my plugins folder. I have also increased my WP memory limit with the code below that I fount on another thread but this did not help.

Added this code to my wp-config.php:
define('WP_MEMORY_LIMIT', '96M');

Could someone please take a look for me at what is going on here?

Support access is ACTIVE until October 19, 2015 7:13 pm

Thanks,
William