Not sure but it could be an allergy.Maybe to the puppy food.Is she itching or scratching?
Have they or you contacted the breeder?
If it was a licenced responsible breeder,they will want to know what's going on with the puppy and how things are going on.
Have the kids taken her to a vet?I wouldn't wait till you took her.
Also,please don't take this the wrong wat.Just because she has papers,it doesn't mean she came from a licenced reputable breeder.A backyard breeder can register pups.
"A dog can express more with his tail in minutes than his owner can express with his tongue in hours."