I just posted this in another thread, it really works on aphids, spider mites, thrips and gnats.
Take a spray bottle, cover bottom with dish soap, fill 3/4 with water, 1/4 white vinegar. Shake gently, spray all over your plants make sure you get under the leaves as ths is where the mites hide, leave on overnight. And don't get the plant dripping, just nicely covered. Next day rinse off your plants with clean water in the spray bottle until dripping clean again. This should do it. Good luck.
PS. I would also disinfect the grow room (take the plants out first though, lol).