Have you tried a good quality grain free pet food without potatoes ? Also a bit of coconut oil orally would help with yeast. And a probiotic would also be a help- I'm using Probiotic Miracle that I got from amazon.com. Purina Fortiflora is recommended by vets, but more expensive. A good antifungal shampoo containing ketoconazole eg. Curaseb would help clear up yeast as well