One of my pullets died this evening. I found her dead in the corner of the brooder box. I have no idea what happened to her. She was part of my very first hatch born April 4th so she was 3-1/2 weeks old. I put the group of them outside in a chicken tractor every day for a few hours. They all seemed to be active and healthy this afternoon when I put them out and also when I put them back in the brooder box tonight. I can't see anything wrong, no blood, no injuries or trauma. All I can think of is that maybe she ate something bad when they were all scratching around in the chicken tractor. They were on soil that is under fir trees so it is kind of loamy. Does anyone have any ideas what might have happened? What should I be looking for that might give me a clue as to what happened to her?