That is the worst, I feel for ya man. I fought them for years, they just kept coming back. I tried everything, then I started mixing 1.25 ml 29% peroxide per 1 L in a 4L sprayer, i just sprayed everthing twice a day for about 2 weeks.
That was about 5 years ago, I just spray that same solution once every 2 days over the mothers, fathers, veg and early flower. I haven't seen them since. Its been a life saver, I've even fixed my Virginia Creepers with this method.
I prefer this to sulfer burners, Safers End All,
Avid and various long chain fatty acids amongst the many others that I've tried. Peroxide is the only one that you can use with a high frequency to match the mites life cycle, as soon as they start to come out of their eggs the peroxide oxidizes them. You can watch it happen under a scope :)
Couple this with DE and its very hard to beat.
Ive learned a ton about them, they can switch their genomes (or dna helix, i forget the mechanics of it) to become resistant to chemicals, that's why you have to keep changing pesticides, not with the peroxide. The eggs are still left viable though, that's why in 2 days you spray again, and again in 2 more and so one and so forth until you win.
I really hopes this helps you. I fucking hates those assholes, its like they are from outer space.
Cheers.