I would for sure take the infected snakes (if it has spread) and place them in another location until you are 100% that they are free of mites... mites can cause come a whole lot more problems than just being annoying, to include spreading bacterial infections.

"Hot Shot" No-Pest strips work pretty good as a preventative, as well as to get rid of them, you can find them at Lowe's or Home Depot in the pesticides section, make sure that you do not place them inside the tubs, depending on the size of your collection you can cut the pest strip into sections and place it in random spots in the room that you are keeping your snakes in....