I'll be honest with ya. I get this from time to time, and I have no fucking clue what it is.
Adjusting PH doesn't seem to help it.
Calcium and Magnesium supplements don't help it.
It's not caused by bugs (at least not in my situation).
My plants do seem to grow out of it. I just figure it's genetic since no matter what I do fixes it.
Broad mites, maybe but it doesn't fit the description.
I've also treated for broadmites and it made no difference.
I'd love some input if anyone else has some.
Peace.
Tav