I am new to yorkietalk and just got a little yorkie Gabby

I have been reaading about the foods people have posted on here but I do not know if they are good for puppies or have a puppy formula. Gabby is almost 13 weeks old and the food her breader had her on was Purina Puppy Chow which I know is not a very good quality food. Her stool has been loose and I do not know if it has to do with the food or coming to a new home. My vet suggested Science Diet but I have not seen a lot of people on here talk about it! What suggestions do you have for me and Miss Gabby??
Thanks!! Emilee