The meaties will eat themselves to death. They need to be kept separate from the layers. The layers need the feed full-time, but meaties should have it no more than 12 hours per day. Otherwise they will lay in front of the feed and eat non-stop. Keep their water and their feed as far apart as possible so they have incentive to get up and walk. Hopefully the one with the bad leg will be okay. He's just got a couple more weeks to go. With my last batch of Cornish X, I gave them some time to free range most days, and not a single one of them went down on their legs. They were healthy til the end.
Good luck!