I've got a weird problem that's so vague, I don't even know

I've got a weird problem that's so vague, I don't even know how to search for the issue.

A few days ago, at least two separate sites in my multisite had a number of plugins randomly disabled, including plugins from wpmudev, WooCommerce, and a bunch of others.

None of the admins on those sites disabled their plugins manually, and I didn't do anything that I know of.

What could cause this to happen?

How can I find out or track what could have caused this or monitor for future changes like this?