....were these 3 snakes exposed to another snake known to have mites?
...first thing is to in-fact determine if they do have mites...look around the eye-caps, in the gular fold (the split under the bottom jaw), in their heat pits...
...treatment: first give them a good soaking in luke-warm water...the water will cool down to ambient temp...that's OK if not too cool...an hour or so is sufficient for a good soak...allow them to easily submerge in several inches of water...this soak will reduce the mite load...
...this soak will also allow the snakes to drink to take care of any dehydration...
...after the soak, remove most of the water and treat with Provent-A-Mite (permethrin-based) or No-Pest Strip (dichlorvos)...both are sold by LLL Reptile...the No-Pest is available at Ace Hardware...some Pharmacies sell permethrin sprays...treating for about 12-24 hours is enough...placing a heat source at one end of the treatment cage is a good idea if the ambient temp is less than about 80F...
...after treatment, preferably place the snakes in individual cages...keep a sharp eye out for additional mites in the coming weeks...occasionally a mite or 2 may get past this first thorough treatment...crush them if you find any...you may need to retreat but the second treatment can be done in the home cage...
...remember to thoroughly clean and sanitize the treatment cage after moving the snakes to their home cages...
...this ought to take care of that problem...but maybe not your ex lol!
Good luck...
Scott J. Michaels DVM