[InkedMarie]

Anne,
I agree with a vet visit but a) Blue ihas had their share of problems; a quick google search will show you.
Your dog doesn’t need a senior dog food. With the exception of Orijen senior, most of the rest are too low in protein for senior dogs. Pick a high quality adult or all life stages food. I’d say do a slow transition to a new food but since he’s having issues with Blue, use a probiotic and digestive enzyme, slow transition anyway & expect tummy upset.