My 1+ year old polish hen was acting normally yesterday. She was let out for some supervised freedom, ate some chopped up kale and oatmeal. Ate some feed (organic non-soy pellets). Tooled around the compost pile with everyone else. When back in the run, she sat in the nesting box for quite a while, did not lay an egg. When I returned a couple hours later, she was still in the nesting box but no egg. I thought she may be going broody, but so I decided I would just watch her on and off the rest of the afternoon. She got out of the nesting box at some point and laid on the poop boards. She is usually very skittish about being handled, but she was very lethargic when I picked her up. I checked to see if there was possibly an impacted egg, but didn't seem so. Her crop seemed okay. There was a bit of whitish/brown poop on the feathers back there, so I soaked her in a warm sitz bath for a bit, dried her off and moved her to a small cage with water and food available and a nesting box. When I returned in the morning, she was not moving and was panting, her wings spread out. When she saw me she fluttered around the cage. Then she died. There was some greenish/brown loose poop that was expelled and also some yellowish bile liquid that came out of her mouth. None of my other chickens seem ill. But, of course, I will be waiting to see if we have a repeat of this. Any ideas what could have caused this? Could it be something she ate? Or could it be an infection that will infect my other 7 chickens? Thanks for any info.