when i brought layla home.. she was not eating high quality food... purina puppy... i switched her to Iams.. not knowing it was also crappy food... however.. higher up on the scale than purina... so as the quality of her food improved (we are now eating holistic) the poops have gotten harder... which is ever so important for their anal glads (we have first hand experience there!) i'd suggest.. once your pup settles in to start slowing changing her food.. unless of course she came on a high quality.
if that is the case.. i cna't help out.. it may have just been a fluke that laylas poop changed with her food.