Have you tried canned pumpkin, broiled chicken, probiotics, goat's milk, or digestive teas?
I'll be the dissenter here, and say I think you did the right thing going off Hills. I also think wet food is superior to dry food for several reasons, including that dogs enjoy it more! I have a degree in human nutrition, and I think that human and pet food is moving in a better direction in terms of re-embracing whole, unprocessed foods we were meant to eat and moving away from the way we have been eating for the last 50 years or so, a way which has caused more illness and obesity. That said, I can see from this board that many people have dogs that live long, healthy, happy lives on various brands, including Hills, and IT'S A DIFFERENT MATTER when the dog has a special condition and may need special prescription food. I completely agree that food changes should be made slowly though.
I'm really lucky with Moxie. I can rotate wet and freeze dried raw food, raw food (and very rarely kibble), different brands (I like Weruva, Stella & Chewy, Primal, Zignature, Nulo, I And Love And You), dog appropriate people food (say, mashed up chicken and broccoli and sweet potato) and it never causes a problem. On the rare occasion, she does have stomach upset, I'll use probiotics, goat's milk, etc, and they have always worked so luckily I haven't needed to try anything further like medication or prescription food. She naturally has an iron stomach (she eats the nastiest things and is fine, I mean vomit on the street
) but I'd like to think the food brands I've chosen are good for her overall health and helps her immune system, stomach stay strong. When I first rescued her, she had thinning hair, dry patches on her ears, diareah, and reverse cough/ sneezed more. Changing her diet helped with all of these things.