Ditto what Diane said.
Getting puppies clean of worms and other parasites and keeping them that way can be difficult. Puppies are very oral fixated, they want to mouth, eat or chew on everything. If they are taken places that other dogs, birds, critters have been you have an opportunity for them to easily get reinfected. Different type of wormers get a variety of worms and the best way to know for sure that you got them all is to check. Yes the "fix" in diet may be showing an improvement, it should, but if the puppy is packing a parasite load or has another problem you still have a base situation that is not going to go away without intervention no matter how well you feed. Considering how much the potential of your puppy's future, both physically and mentally, is decided by what you do this first year, a trip to the vet is a solid investment in it's future. If there's no other problem, great, if there is, you have caught it early and can limit the potential damage it can do. Good luck and a long and healthy future with your pup!
