So try something. Ban neonicotinoids in some state like Washington. Monitor progress closely.

The current situation is like having a bug that only shows up in production. At first it wasn't so bad, but we're in day 8 and now half the data is disappearing.

You can't identify the cause without getting in there and trying things. Change. Monitor. Repeat. With a solid lead (and we have one with CCD), it is the quickest way to solve this problem.