I have (correction had) 8 young adult hens and one rooster. Now I am down to zero roosters and 4 hens. They are coming up dead. No signs that anything has gotten to them. At first I thought maybe hens were dying due to laying eggs. They were just getting to the point of egg laying so I went and bought oyster shell. Next the rooster died and today another hen. So that can't be it. Any suggestions? They do not roam freely and have a pretty good size pen and coop. Thanks in advance.