Most folks recommend keeping the puppy on what the puppy grew up on and not switch for some time as the pup is having enough major changes, leaving mom, littermates and all that he's ever known.
One of the breeders can add what they consider a reasonable length of time. Anthony kind of ate anything as his breeder is a vet and there were lots of samples! Stella is a rescue and she was on Beneful:-)
Today they are both on Fromm grain free.