That sucks!
I'm not sure, but I think it's definitly too late for any chemical stuff! I don't know if some other mites, that kill the spidermites, or any other kind of flies that kill them will help in that late stadium!?
Perhaps some completely dipping in water.
I heard of some stuff, that is mostly used for pets, but can also used for people, to get away, ah damn I don't know the english word, little fuckers that are on your head and every where on the boudy, if you don't wash yourself! Hope you know what I mean!?
I heard that can help, but it's late.
All the best, hope anybody else can give you better help!
Good luck!
Tolpan