If you're less then 3 weeks into flower you can use a product called SNS-217 which will kill live mites and eggs. Some lady bugs won't hurt either. You can also try Aza Max and just feed it to the plant so the roots suck it into the plant, it will act as a systemic and once the mites bite into the plant they will die. But this is a long term fix not really an immediate fix.
Try pyrethium just apply it carefully...I know it sucks balls to use a spray during flower but I've done it when I had to, and used this product and didn't have a negative effect on my buds.
Other people use neem, and rub it on the leaves.
Remember prevention is the key to avoiding pests. Fix it before you get it, and life will be easier on you and your plants.