My 11 month old bulldog is having some skin problems. I need some advice. The spots are round with hair loss very itchy. He has 4 sposts. I have taken him to the vet to have tests. No mange he had that before. She gave me some stray it works until I stop using it. I don't see the hair growing back. He is on Fromm dog food which is grain free . He is getting fish oil, Vit C, Zinc and E after he got mange. Any advice what else I can do.???