It's the Player's Deal. They are the ones that need to take responsibility for this. It is hard work to be in really good shape when you are also trying to put on weight and be as big as possible. It's their fault if they just work a ton in the weight room and not enough on cardio.
Speaking as a former O-Lineman who played at smaller schools in college, it is a year round job. My cardio training was something I worked on all year long. I played at 6'3" and 285 lbs. Had I let myself just plump up, I would have played at 305. It's all on the players.
Sure the SC coach can give them different programs to do, the position coach can get after them. But ultimately it is on the player.