Two WPMUDev plugins break my theme (Divi, from ElegantThemes).

When I installed CoursePress Pro and Appointments Plus, my theme (Divi, from ElegantThemes) is seriously broken. The elements on my pages are mixed up, the alignments are out of order, the size of testimonial boxes are much smaller, etc. This seems like it's probably a CSS issue, but I'm really not great at CSS, otherwise I'd probably take a stab at fixing this. Is there a simple fix?

When I disable both plugins, my site's layout goes back to normal. And when I disable the two plugins singly, one at a time, some things are fixed but all.

I really need these two plugins. Can you help?

Thank you!