I can tell you that NutriSource is usually easy to transition to and doesn’t usually cause upset stomach, so it might be a good one to try. Did you do a slow transition from the old food to the new one?
Constant diarrhea is not healthy, no matter what your vet says. I wonder if he had a large load of worms as a pup or if he had some other insult to his intestines. Or he may be developing a food intolerance, so watch for other symptoms to show up like gunky eyes or ears, itching, hot spots, rashes, oily coat, funky smell, gas. If I were you, I would get some Perfect Form from the Honest Kitchen and start them on that. It has some great ingredients for calming, soothing, and healing the gut.
