it could be spider mites. they will severely damage plants if they are not removed.
i had an infestation of those in my M. Betsileo tank a while ago, and the onl way to get rid of them (without hurting the frogs) was to tear down the tank and replant it with fresh, new plants and substrates.
when you spray the enclosure, can you see any "webbing" around the plant bases or stems?


