Could be he has an allergy to something in his diet and it could be upsetting his little system. Was this what the breeder had been feeding him before you brought him home? Or did you just cold-turkey and give him this Innova diet upon bringing him home? Could be a number of things. Things to definitely watch out for is blood in the stools. I would call the vet if you have not already done so and maybe take in a sample of the stool to have checked out. Also make sure he is drinking enough water as they can dehydrate so quickly. Good luck and keep us posted. Hope he improves soon!
