If a puppy is severely infected with parasites, it can vomit them. There was a GSD puppy at the vet clinic I worked at many years ago that was HBC. After surgery while the pup was still sedated, the parasites crawled from his mouth and anus. It was the worst infection I had ever seen and probably ever will see. Fortunately for that little guy, his owners never returned and he spent the next 10 years with me

Please take the pups to the vet. The treatment for roundworms is relatively inexpensive in the great sceme of animal medicine.