We have 5 chickens and we went out the other night to put them to bed and one was dead. She never made it up to the coop to roost with the others. There were no visible signs of injury or animal attack. She had not been exhibiting any signs that anything was wrong leading up to her death. She was a 2 1/2 year old Plymouth Rock and that seemed young to die of natural causes or old age. I am very concerned about loosing my other chickens if there is a chance that she had something contagious. I noticed today that two of them had diarrhea, but it has been almost 3 days since she died and they are all doing great and seem totally normal so I have no idea if it is related. Has this happened to anyone else? These are our first chickens and our first experience losing one. I would really appreciate any insight that anyone has. Thank you.