To deal with mites, you have to think genocide. You have to wipe them all out and can't leave any left!
Start with an easily absorbed silica nutrient supplement. I use Dyna-Gro ProTekt. The plants use silica to reinforce cell walls, causing bugs to wear down their mouth parts faster every time they take a bite.
Silica will not cure spider mites, nor will predator bugs, they will only help, some.
A lot of people use heavy duty poisons to make their plants immune to mites. Forbid, and AzaMax come to mind for me, but there are others as well.
Personally, I've never used poison, I prefer an organic approach, but this only works when in veg. I would not attempt in flower. Here is my own organic soap spray:
Put this in a blender and liquify:
1 cup of water
3 cloves of garlic
1 teaspoon of cinnamon
1 teaspoon of chilli/hot sauce
1 teaspoon of rosemary
1 teaspoon of clove
Saute the mix on the stove for about ten minutes, then strain, and add:
enough silica supplement to pH buffer (hot sauce is acidic)
1 tablespoon of diatomaceous earth (this stuff is dangerous to inhale, so definitely do not add if flowering)
a few drops of dish soap
You can also add Neem oil to the mix. I've never used it myself, but I've seen it used successfully.
Put the mix into a spray bottle, top off with water.
Apply every day or two for at least 2-3 weeks. Make sure to coat the undersides of the leaves, leave no surface un-sprayed!
Keep applying after you see no more mites, make absolutely sure there are none left!
Also, regularly clean your grow space and around it with a bit of bleach in water, every week at least!
From this point on, you must take preventative measures for your girls in veg, apply neem oil and/or some other bug killing agent as often as necessary, and keep a close eye on your flowering girls!
It hasn't happened to me yet, but if I had girls infested late in flowering, I'd toss 'em, make sure my grow space is sterilized, and start a new batch of flowering girls with a new set of clones.
Good luck.