Hi Lewis- Congratulations on your new pup!
There are many reasons your boy could be experiencing diaherra with Blue Buffalo. Though your other Pugs didn’t have issues with immediate switches this one is a new dog with a different GI tract and he’s also a young puppy. Because stress can cause disgestive upset in young puppies after coming into their new home, it’s advised to continue feeding the same food the breeder had him for a few weeks and then start introducing whichever food you’re interested in feeding.
I’d suggest going back to the Eukanuba formula for a few more weeks and then trying to add the Blue back- very very slowly. If he is still experiencing digestive upset then it’s time to consider that one of the ingredients in the Blue Buffalo formula does not agree with him.
