Proplan selects is NOT a good food by any definition. Not the worst, but it's one of those bags of rice spiked with corn gluten to pretend it has protein in it, and a bit of meat, turkey in this case, to pretend it has meat in it. I'd suggest the OP change foods just on the basis of the ingredients and the huge amounts of poop. Just try one of the foods suggested for a couple of months and see if the pup improves.
Proplan select puppy Ingredients:
Turkey, brewers rice, corn gluten meal, chicken meal (natural source of glucosamine), pearled barley, animal fat preserved with mixed-tocopherols (form of Vitamin E), oat meal, dried egg product, pea fiber, dried beet pulp, fish oil, animal digest, potassium chloride, calcium phosphate, calcium carbonate, salt, dried tomatoes, blueberry pomace, dried sweet potatoes