alright so i have to take action. I have heard good things about mighty wash too and that you can use that close to harvest with no negative effects would that be another choice because id rather not pepperspray my ladies.
Mighty wash is worth a try I suppose. 2yrs of chemistical engineering and I have no idea what the science behind it is. From what I understand its greater than 90% water and the rest of the contents are inert. However it can't hurt. Be sure to let us know what your results are. From the little bit of research I did it seems like the community is very polarized about its effectiveness. Some people think its hocus pokus, others swear by its effectiveness. They use something called "frequency adjusted water". I can't think of what that might mean other than it somehow uses the resonance (electromagnetic I would have to guess) of water to kill spidermites.
This is purely speculation based on very little knowledge but;
Maybe they have found some combination of inert ions that when combined with either hydronium or hydroxide in a solution changes the fundemental frequency of the solution to something close to the emmission spectrum of grow lights, and when the spider mights absorb the solution their naturally chemistry is changed.
I doubt I'm right, but its an idea.
If the mightywash doesn't work out the pepperspray method is fairly safe for you plants. However before harvest I would go ahead and drench them with pure water so the pepperspray doesn't end up in the final product.