Well, Karla pretty much said what I was going to say. How many shots has the puppy had? If this is Parvo, puppies can die from that quickly.
Hope you can work something out.
Adult food probably did not cause this reaction! Since your puppy is not old enough to have had all it's puppy vaccines & there is not a 100% guarantee either way. I would be worried that this is the beginning of Parvo.....If it is, then your dog is in the middle of a life or death situation.....
Without medical treatment, death is the result!!! A simple fecal test from your Vet will give either a positive or negative for the virus....
I suppose when you got this puppy that you didn't allow for the possibility of needing funds for Vet emergencies..This happens all too often!! Please, find a way to get your guy to his Vet......He is depending on you for his needs for life!!! Make the call, now......Good luck, Karla