I agree with Elaine. My own experience with interdigital cysts is that they flare up depending on the season. I had quite a bit of trouble with them a while back and then they pretty much disappeared, only to return on one toe yesterday (not too bad, however).
In addition to what Elaine said about the bleach soak, I would be sure to wipe between his toes every morning with a malaceb wipe. This is a part of Bully's daily grooming routine and he seems to enjoy it.