James Wellbeloved Lamb is probably the best you could buy for him at this age, its a very good adult food too, Id take him off the hills and youll see an improvement immediately. My pup was on Beta and a lot of pups are given it, I changed mine to Burns at 12wks as he was having fits of energy that just would not stop until he exhausted himself, Burns cooled him immediately and improved his attention in training. It does keep dogs lean though, so with a lab id expect youd want a few lbs on him which is why I say JWB
Orijens tip top, so maybe look at it when hes 6-7 + mths? you wont find a better food really apart from a well judged BARF diet..??