This past summer it was so hot our puppies had mites which attack hair follicles. All the hair on their tail came off. The Vet gave us some medicine to use which killed the mites. He said it was due to heat and stress from the heat. We never experienced that before. Even now that the weather has cooled some of our puppies get a real crusty patch on them. We have been using an over the counter med containing 2% Nitrate and it seems to work. Although we can't figure out what causes it.
IT SOUNDS LIKE YOUR DEALING WITH DEMODECTIC MANGE. DEMODEX IS A MITE THAT ATTACKS THE HAIR FOLLICLES. YOU SEE IT TYPICALLY IN PUPPIES OR SOMETIMES OLDER DOGS WITH UNDERLYING ILLNESS. IT CAN BE GENETIC, BUT YOU TYPICALLY SEE IT MORE COMMONLY IN CERTAIN SHORT HAIRED BREEDS SUCH AS PITBULLS AND DOBERMANS. MANY ANIMALS CARRY THE MITE, BUT ONLY THOSE THAT ARE IMMUNE SUPPRESSED WILL EXPERIENCE SYMPTOMS. ALSO, IT IS NOT CONTAGIOUS TO HUMANS OR OTHER PETS:) TOPICALS GENERALLY DON'T HELP-IF IT IS A GENERALIZED CONDITION (OVER SEVERAL AREAS OF THE BODY) YOU'LL PROBABLY NEED TO HAVE HIM MITABAN DIPPED.
I would take them back and make sure it is mange, or if it's staph, because the treatment you are givng will not cure either, and the nitrates are toxic. If your vet does a skin scraping, he will be able to tell what this is. It should have been completely cleared up by now. Good luck with them.