Sorry for your loss. There are many ailments that a 5 year old hen could suffer from. The drooping wings and tail, and acting lethargic are universal signs of a poor feeling chicking. Dehydration, several different reproductive disorders including internal laying, egg yolk peritonitis, ascites, crop problems, and heart failure are common. Your state vet could perform a necropsy on her if you refrigerate her body and ship it to them. Some things can be discovered with your own necropsy at home. Many people here can look at pictures to help you .