I am currently raising my fourth flock of chickens and my chicks are currently about 2 1/2 weeks old. Apart from pasty butt during their first couple days (which I of course took care of), they seemed to be healthy and happy. They always have clean food and water and a light for heat. However, after checking in on them for the last time of the night I noticed that one of them was dead and stiff (had checked on them previously no more than an hour before). Not sure what to do or what it could be. This is the first chicken I have lost before the age of 20 weeks. Any thoughts or recommendations? Thank you.