OP, puppies grow quickly, so they can stand to be plush at this age. I don't believe in keeping puppies skinny anymore than I believe in putting infant children on diets. Pups can catch a bug fairly easily, because of their immature immune systems, so I'd prefer to err on the side of having a plump puppy vs. a skinny one. My now 8.5 month old was eating about 7 cups a day of fairly calorie heavy food at your puppy's age.