If your hens' backs are "beat up", I think you've anwered your own question. Check to see that the roosters toenails and spurs are not lacerating the sides of the hens. Sometimes in competition for breeding roosters can seriously injure the hens backs. Most of the damage usually occurs on the sides just in back of the wings. Left unattended these wounds can become maggot infested and cause the death of the hens.
