It's a bit odd for a 5mo old cockerel to stay away from the ladies, but you are finding him in the coop eating/drinking instead of foraging with the girls - the first thing I would do after an inspection is give him some poultry vitamins and extra protein. He may be lacking in nutrition.It’s the Dumor layers feed And I mix some Purina layena pellets omega-3 in there. And they free range.
Personally, I prefer to feed an all flock/flock raiser feed instead of layer feed. Too much calcium in layer for cockerels/roosters and I feel they need a bit more protein.
What breed is he? Do you have photos of him?
Also...is this the same "group" that you were asking about how to treat tapeworms in the other thread?