I went out to my coop thismornin and found one of my chickens laying on its side with its eyes closed. I thought it was dead. When I picked it up it opened its eyes, ruffled its feathers, and curled its neck back. I brought it in the house and about 20 minutes later it died. I hadn't seen any symptoms before thismornin, it was just all of the sudden. Does anyone know what could have happened?