Website crashing after adding WPMU DEV Plugins

I have a tech-guy setting up Membership 2 on my sites and he noticed the site continually crashing, he said there were too many add-ons with WPMU so he removed them.

I am not the person to ask technical questions, I am trying my best to troubleshoot as I go…

So he has removed or disabled WPMU plug-ins (that WPMU suggest to add on joining their
membership) and then the site started crashing.

Is it a WP Version conflict or other I am not sure. Ask me how to improve your emotional well being, that I know, computers and wordpress are not my bag…

So I need a techie with Guru powers that can set my wordpress area straight!

Regards,
Stuart