Keep an eye on them but hold off spraying, since you're so close to harvest plus as I understand it they really need warm, dry weather to thrive. Matter of fact, if it won't rot your buds, maybe try misting or spraying with water, as some people say the moisture really messes up their life cycles. In fact, I've seen special hose attachments that allow for spraying under leaves and the companies that sell them claim they are great tools for getting rid of mites. But those are for general gardening purposes, not specific to cannabis. So it would work fine on a rose bush but I'm not sure it would be a good idea for your plants at this stage of flowering, due to the possible mold risk.
Another thing, don't laugh but I've heard you can just blow the little bastards off your plants with a hair dryer or leaf blower. Since you're growing outdoors, I'm betting that you've got natural predators that are already helping to control the fuckers. So, if you just dislodge them from the plants, they have to trek through "miles" of hostile territory to get back, and a lot of them are going to get eaten before they can return. In theory, at least.
