She'd have been 2 this April. She was laying regular up to being broody. She was "broody" for about 3-4 days (walking around puffed up and clucking) before she finally sat on the nest, so I knew it was coming. She's not thin or bony at all... She was warm when I took her off the nest today. I've flashlighted her the best I can without disturbing her dying, and I don't see any wounds or lice/mites.
Her entire body is cold right now, even though the house is 75 and I'm right next to the wood stove (that's on). Her breathing is shallow, her head is hanging down off my lap and her comb is now purple.
She has no power to move her body at all.
That sounds like a heart defect. If she's having low oxygen...well, it's common with hatchery stock. Is she from a hatchery? I experienced this with 2 and had necropsies done, and then I knew with the next one. I haven't any more hatchery stock an haven't ever had any live more than 3 years. I'm so sorry!
edited because my hands are confused
I agree with Renee about the heart problem. The purple comb is a symtom of lack of oxygen (I've seen this from the Cornish X meat birds that I've raised for the freezer) and have seen rapid death once the comb darkens. I would have to think it was something she was born with that manifested at this time, most likely not related to her broodiness or something she ate or anything you did.