Just switch to plain tap water, at about room temperature- it should be refreshingly cool if you stick your hand in it, but not cold. Cold water can cause funky soil chemistry.
That's the strangest symptom I've seen yet. It looks like Zinc lockout, but too white!
Make sure your water is the correct temperature, stop using your Brita or whatever, and only water when the pots feel light.
Next time the soil gets dry, do a runoff test by testing your water pH, then pouring it through the pot and testing what comes out.
Report the results of both tests.
I'm only chiming in now because you described mite damage perfectly, but the pics show something weirder.
FYI, charcoal filters remove particulates and organic compounds, such as chloramine and other disinfectants, but do not remove dissolved ionic substances such as Ca and Mg in any appreciable amount.