My rottweiler is a picky eater, which is odd for the breed, so it is sometimes difficult keeping weight on him. My sitter ran out of his diet while I was away, and so I picked up a bag of Purina ONE™ Large Breed Adult Formula and he gobbled it down. He just turned a year old, should I be worried about his lack of size? He is a show dog from very good bloodlines, but he is lacking height, I work for a vet, but somehow I think I must have done something wrong. Any words of wisdom?