I have 18 Cornish X that are 6 weeks old. My roo's weigh in at 8 pounds now. Both hens and roo's are looking healthy and moving around fine, but they are "plopping down" harder and more often than they used to. I'm trying to decide whether it's wise to try to keep them alive another week for the extra meat, or if I'm going to run into trouble and lose some. Does anybody know at what age the leg/heart troubles really begin?