Does he have any signs of Mareks disease, such as lying with one leg forward and one leg under or back? Does the bad leg seem numb or paralyzed, and does he use his wings to balance? With 2 roosters together, he may have been injured, or he could have been born with a leg issue or leg bone deformity. Varus or valgus deformities are common and may cause one or both legs to become bowed in or outward. When I have kept more than one rooster in a flock the subordinate one always seems to become weaker. Hard to know what exactly is wrong, but watch for the other rooster who may pick on him as he has leg or walking issues. It might be better for him to be in a wire dog crate or pen with food and water. Watch out for breast blisters or callouses over the keel/breast bone which can happen with continued pressure over the keel bone.