Okay, you all suggested different things, so fuck it, I'm going to try something different too.. Picked up a tiny bottle of Avid. I know, I know, poison, cancer etc. But I didn't want to fuck around. I won't use it next grow though, I'll rotate. Responsible miticide use. I've read that Avid is pretty safe to spray 45 days before harvest, so that puts me at September 11th, right around day 60 flower.
Thanks for all the advice, and I'll definitely refer to it again someday!
Edit: Post-spray once-over shows no mites. I also hosed down the tent a little and will be shop-vaccing the fuck out of it in a bit. I have a few little spills of perlite, and mites love mess..