I have found that a good soaking will kill many of the mites. Also a thorough cleaning of the cage, spray the cage with pest/ insect spray & leave overnight then clean again & re introduce the snakes.

Another method is to place a small piece of pest strip in a sealed perforated box & leave in the enclosure for a few days. The vapors from the pest strip kills mites. Just make sure the snakes cannot get to the piece of pest strip & remove the water dish while the pest strip is in the cage.

Repeat the process over the next few weeks or each time you see mites. LLL reptile sell a mite spray that you can wipe over the animal also.

Hope this helps,
Andy.