9 week old puppy - diarrhea

Question
We got a golden puppy 2 weeks ago he is now 9 weeks old.  First week he was fine - had been eating Mom's Eukanuba, we mixed that with Pedigree dry & moist until we ran out at end of 1st week.  Threw up w/diarrhea after week and 1/2 but seemed fine otherwise.  Have had diarrhea since, 3 days ago switched back to Eukanuba puppy and diarrhea went away.  Today he had black poop and 1 diarrhea movement.  Should we take him straight to the vet?

Answer
Black poop can indicate bleeding somewhere in the intestines, usually in the small intestine.  That can be caused from things like hookworms. Your vet will be in the best position to evaluate this and to treat it. He will need vaccinations anyway at this age so take him in. Many puppies are "Allergic" or sensitive to many dietary components, so if he does well on one type of food, then I would stay with it.