Yeah if you can't get a hold of the breeder I'd take him to the vet. Don't give up on the breeder though...you need to at least know when he was vaccinated. Feeding puppies is by no means an exact science. Our GSD never ate puppy food, although we did have a prolonged guess and check experiment with several high quality adult foods before settling on "the one". Also, never had any success with wetting his kibble. It tended to leave him bloated and gassy (he even regurgitated a couple of times). That is not to say that any of this is "bad" per se...it's just different for every dog and it's all about finding what works for you and your pup.