I Do Not Know What Disease My Chicken Died From

[Poultry Maid]

Hello, I have a flock of nine chickens and today one of them died She is a Golden Comet about four years old. This past week she was looking very sluggish and sniffling. She was also very skinny even though she was eating and drinking a lot. Her feathers looked ruffled and she kept to herself. She also kept her eyes closed a lot. Just before she died she started stretching out her neck and gasping for air. She started violently tossing herself across the ground and then died. Her poop was green, but her vent was clean. The rest of my flock appears to be their normal selves but I am worried they will get whatever she had. Does anyone know what disease my chicken had? I Am finding it hard to narrow it down.
I appreciate any ideas!

 

[ChickenCanoe]

Those symptoms are common for a great many things. Too numerous to mention.
The only way to know is to send the bird off to your state poultry lab for necropsy.
What state are you in?
ETA
You could also cut her open and post her yourself but I imagine you don't want to do that and you still wouldn't be able to do cultures and other lab work, just look for organs that don't look right.