This morning I went to the brooding coop to let the babies out to range and found 2 of my WyanX chicks dead on the floor under the heat light. They were probably around 5weeks old, a little pullet & roo. The only sign of feeling ill they had shown was looking a little bit cold. I had to move the pullet indoors a while ago and she had been just fine since i moved her back outside. I moved the little roo under their light yesterday and he settled in but still seemed lethargic maybe? This is the ONLY sign they had showed. I havent seen and bloody poo in their coop or any other symptoms of anything. There are also about 5 other chicks outside with them that are perfectly healthy. they run the yard, eat til they're stuffed and them come cuddle in with their duckling buddies at night for bed. they even cuddle in the duckling piles around the yard during the day. I also checked for mites/lice and there's none. Any ideas what happened to my babies?