I have several chickens, some 1 and 2 year olds, and some chicks----from 2-3 months. 2 of my NN chicks have died this week, with no noticeable symptoms whatsoever. When I found the first, it was barely alive, sitting by itself and peeping-----it died not long after, but the only thing I could see wrong with it was that it was extremely thin. It's breast-bone looked skeletal, and I could plainly see it's neck bones. The same with the 2nd one that I found already dead today. Before they died, they seemed perfectly fine......eating, drinking, and walking around. I feed my chickens very well, and all get their share. How could this happen? Is this some disease? I checked some of the others, and did find one that also seems thin.