Henry is currently eating Merrick Cowboy Cookout kibble (beef-based.). He has done okay on it, but has never had truly firm poop consistently. He had a bout w/ diarrhea yesterday & the vet prescribed Flagyl and fortaflora. Fecal test was clear. He is on a bland diet of boiled hamburger and rice for a few days. If I was to switch his kibble, now would be the time, as I will be gradually adding it in with the beef and rice. He doesn't do well on kibble with chicken. Any suggestions?