My 6-7 week old flock of 10 spent their second day free ranging and went into the woods behind their coop. At sundown, they all returned to their coop looking fine. When we went out in the morning to check on them, two pullets had mysteriously died. There were no signs of trauma. Their vents were clean... No marks around their necks (I read somewhere on here that was a way to check for...something?) I think heat related death is unlikely. I'm in North Texas, so while it was dreadfully hot, they had access to water and all seemed fine by the time it cooled off in the evening. From what I can guess, they probably ate something poisonous, or gnats suffocated them in the night. We moved a bug zapper near their coop to prevent the gnats...but I want to make sure I'm doing everything possible to protect my remaining 8. What else could have killed them? For the time being, they're penned up, but they seem so much happier when they're free ranging and catching lots of bugs. Are there any ways to keep them from eating things that are poisonous? Please advise!