When I have to deal with the dreaded mites I use this:

1/4 cup Baking Soda
1/2 cup Apple Cider vinegar
1 Tablespoon Lemon Juice
2 drops dish detergent
1/4 Teaspoon Epsom Salts

Take a cup of very hot water and dissolve the Epsom salts,take rest of ingredients and place in a clean 2 liter bottle and let work out. Add Epsom solution. Add water to fill to 48ozs(3/4 full). Shake well.

TO USE: Cover soil/medium with plastic,with lights off mist plant all over, especially under leaves,

Wait 20 mins, then spritz off with clean fresh water shaking as much water off plant as you can.

The fresh water spritz rinse will remove the solution along with the dissolved remains of the mites and their eggs. This is VERY important any remaining solution can cause a mild burn to the plant, not to mention who wants to smoke dead mites and such.

Watering the plants 1/2 hour before spraying will help keep your plants from absorbing the spray.

Recently used on some ladies 7 weeks into flower with no harm other than browning a few hairs which were shortly replacecd.