I went out to my coop this morning and one of my barred rocks that is probably around a year and a half old was dead. Her eyes were closed, she was in the coop, nothing looks amiss, and all my other chickens (8 left now) are just fine. I am told that it is common for chickens to have heart attacks. Is this true? What is a common cause of death when the circumstances are like this? Thanks for your ideas.