I have 50 meat birds (cornish) they are 6 weeks old and the majority of them are doing fine. But in the last few weeks several of them have become lame. The birds are free fed med-free grain. They coop has a 1/2 by 1/2 wire floor but they are let out everyday to range in a fenced in area. Right now I'm seeing a 10% affliction rate and that seems way too high. Can someone out there give me a clue as to what I may be doing wrong? Thanks for any help.