We have lost three chicken so far. These chickens are pets. They go into their coop at dusk and are out all day. We feed them scraps and chicken fed daily and have plenty of water available for them at all times. Our problem is their "tail" starts to "droop". They act normal, eat and drink, it takes about three weeks after we notice their tails drooping that they die. Help! They are about three years old. Thank you.