Last night about 6pm I closed the coop on our 8 chickens this morning about 8am when I opened the coop all the chickens were dead. there is no sign of a predator there is a small amount of blood on a few of the chickens around the head. They are about 18 weeks old and we got them as day old chicks. they were out of water this morning but had some water when we put them up and have access to water all day long as they are free range with a outside waterer and an inside waterer. could being out of water for a few hours kill them? the weather was about 40 degrees f and rain storms. the coop is 1/2 of a baby barn 4x8 and an additional 1x3ft nesting box.any help to find out what killed them would be appreciated.