What's wrong?

[Usedtowanna]

I went to let out the chickens and discovered a chicken sitting OUTside the coop in the yard. She can't stand, is panting and has a poopy butt (maybe because she can't stand to poop?). She is almost a year old. No signs of injury anywhere.

 

[MysteryChicken]

Internal laying, advanced stage before death. Experienced the symptoms before my favorite hen died, & discovered the cause after I did a necropsy on her.
She also had a ruptured egg gland with broken shell-less egg inside her.