Yesterday, I came home from work to let my girls out of their pen, and one of my hens was dead as a rail. They were running free all weekend long. I keep them locked up while I'm at work, since I can't necessarily protect them if I'm not there. So I'm not sure if she had gotten into anything over the weekend? All of my girls seemed fine Sunday and Monday morning before I went to work. These girls aren't quite a year old yet. They're right around the year mark though. A few weeks ago, we had placed some "littles" outside. They're still separated from the big girls, by a run and chicken wire, but they can all see each other. They were segregated from the big girls COMPLETELY, for about 7 weeks before they got to meet through the coops. I am still new at this backyard hen thing. My Big girls (the Rhode Island Reds that are approaching a year old) were my first birds and the ones in the coop with the run are only my 2nd batch of birds. I didn't examine the body but she appeared fine. No visible injuries. What should I do? Do I need to quarantine the girls and keep them all separated? Any idea on why a hen would suddenly die? She wasn't having bowel issues that we've noticed. She was laying eggs just fine. The only thing I know that was "Different" was that the boyfriend put out some diatomaceous earth when we were cleaning poop out of the coops. I'm lost on this one and need some advice.