Our 7 months old blue cochin hen abruptly died this morning. She showed no previous symptoms of injury or illness, not even a change in behavior. Her only indication that something was wrong was listlessness and weakness when I opened the coop this morning moments before she died. Her in take of food and water have been consistent, and she showed no signs of any difficulty laying. There are three other birds in our flock, one silver-laced wyandote and two easter eggers, all are exhibiting normal behavior. We have had no history of any illness with any of our birds. They all roost together in a suncast, vinyl shed with attached run. Bedding is straw, regularly changed, and the floor of the run is just the soil and leaf litter of our yard. They eat layena crumbles, supplemented with crushed eggshells, charcoal, and poultry grit, plus vegetable scraps and grass from the yard. Water is available 24/7 and lightly treated with vanodine to prevent fungal growth in the container. We are completely blindsided by this and utterly saddened. Any insight anyone can provide is greatly appreciated as we hope to prevent this kind of thing from ever happening again. Our thanks in advance.