Sick Puppy

Abu has been vomiting for a couple days. "my 10 year old pomeranian".His drinking habits are the same as they have always been, not drinking more than he was, or less. I did change his food to a better quality DF.He has never had problems switching DF's.He used to eat this brand and did excellent on it.He hasnt lost any weight, actually he gained some. He really loves this food.All my dogs are on it, as is my cat. It is very high protien.It is probably the dog food, no? Being that he hasnt had problems before, do you think the bag we got came from a bad shipment? There are no chemicals he could have gotten into, no house plants...He seems fine, even after he vomits.Can it be he has some sort of doggy bug? Maybe just an upset tummy? Thanks,tsavo.