I was recently helping a friend with his operation. Pretty beefy set up. 4 lights, over 20 plants, etc.
I found 1 spider mite infested plant. (Really infested) I checked the plants around it, and they seemed fine. I removed the infested plant, and did some heavy defoliating on all the healthy plants. We are week six into flower, and not a single plant is having pest issues. (I removed the infested plant about 9 weeks ago)
Dense clusters of foilage will promote pest problems. Some growers suggest that defoliation will encourage plants to increase their natural pest resistant chemicals.
I dont know how bad ur mite problem is... but this is my advice: defoliate ur plants. Remove about 30 - 40% of fan leaves. Especially any leaves that have obvious signs of yellow speckling. (Yellow specks on leafs are signs of spider mite damage) Wait 2 - 3 days after defoliating, then spray your plants down with neem oil. Continue spraying every other day for 2 weeks. (Do not spray while lights are on)
If your diligent, it will work. once ur done with all of this spraying, keep an eye on the ladies and be sure to look specifically for any yellow specks on the leaves.
Good luck