definatly keep them away from your snakes. get a tub set up for each one, and order some provent-a-mite. follow the directions EXACTLY. give it a few treatments and a couple weeks, and you should be good. i would still keep them away from your other snakes for at least 90 days.

where are you located, i am sure there might be members near you that would take them from you and treat them, if you don't want to. i wouldn't let them stay in petco any longer then they already have.