I had a black Australorp hen that was about 2 months old. When I went to put the chickens up last night she was hiding from me under the coop so she was left out accidentally. It only got to 65 last night. This morning when I went out to let them out I noticed she was out running in the run. Then within a couple of hours she started to not eat or drink and became lethargic. She was walking at the time but then started to not walk and just laid down. Her breathing became heavy and shallow and within another couple of hours she was dead. Does anyone know what might have happened? There was no visible signs of trauma or puss nor anything. I am at a loss. Now I worried that this might happen to the other chickens. Can someone please help?????