My Australorp has been really lethargic for a week. I thought it wasn't anything major until last night it took a bad turn. She was just standing outside not moving. There was a pile of bright yellow diarrhea under her. I quarantined her and put a heat lamp on her- she didn't even move when I picked her up and bedded right down. This morning I checked on her and actually thought she was dead. Her neck is craned backward and she doesn't move when I touch her. She's blinking so I know she's alive. I attached a picture, any ideas what it could be or how to treat? Thank you.