This may have nothing to do with it but it came to mind when I saw that you feed them frozen mice. I recently took a snake to my vet and had a fecal culture done. We found both mite eggs and dead mites in the stool. My vet remarked that they didn't look like reptile mites and since the snake didn't have mites the best conclusion he came up with was that the mites were coming from the frozen mice. The stool was collected by palpating the snake...so it's likely that there was no contamination. Although this was not the problem with the snake it was really interesting to see under the scope. Sadly, I don't have any pics but it might be something to check into.
W. Smith
W. Smith