At 11 weeks he was probably undergoing a juvenile molt. They outgrow their feathers and have to replace them. The exact age for that can vary but that is why you see pin feathers.
Cockerels and roosters tend to not have a lot of fat on them. Pullets and hens do. That's a sexual thing as...
You are feeding them as if you are in a race to get them to butcher size as soon as possible. You are feeding them to grow as big as they possibly can.
If you want to breed them then feed them a much lower protein feed early on, maybe even restricting feed like you do to Cornish X...