my pup is 9 months old, and the food that im feeding him says on the bag to switch to adult at 12months. last week i had him to the vet and he was 50lbs and the vet said to keep him at that weight. she also toldme to switch to adult food now. first yes he may be done growing but really cant they grow more why keep him at 50lbs, also why the switch to adult food. whats the difference between puppy and adult food? thanks