hummingbird, wpmu dashboard, site broke up, errors

I am not sure if it was hummingbird or wp dashboard that caused this. The site at https://pismorent.com is hosted at wpengine. Perhaps there was a plugin conflict. I deactivated hummingbird and wpmu dashboard to get the site pages to appear normally again. I would love to speed up the site by using your plugins. Can you tell me could have caused the issue and how to get this to work? Thank you for your assistance. It is much appreciated.