Our 8 month old German Shepherd has had diarrhea for about a month. Vet has tried 2 rounds of metronidazole & 1 round Panacur. He didn't have any parasites in his stool sample. We did chicken & rice & got it back to normal texture. We added his Blue Buffalo large breed puppy back in very slowly & he has gone back to looser stools. It has to be the food causing the diarrhea. Any suggestions for what to try next or what to do? It's just puzzling to me that he ate this food for months & now has diarrhea with it. Thanks for the help.