Are you saying that you've seen mites in your tanks? For every one that you see, there's 100 other little bastards crawling around that you don't see.

Look over your BP for mites. They are usually easily seen in between the wider scales on the sides and belly of your snake. Giving your snake a soak for about 30 mins will usually kill off some of them, sometimes thats a good way to tell how bad your infestation is. Lots of visible adult mites means LOTS of invisible small adults, larvae, and eggs.