I would get her off the Pedigree Chum asap, it really is cr@p food.
Good quality dry foods are Burns, Arden Grange, James Wellbeloved, CSJ and Autarky. Good quality wet foods are Nature Diet, Nature's Menu or Forthglade.
Some pups can have a runny tummy when they first come home so I wouldn't worry too much but I would definitely get her off the PC
