Hi, I recently got 4 pullets and I keep them free range. They all look really healthy and are laying regularly. One of them starting acting strange yesterday, she was just standing around and seemed really lethargic and not interested in food. She was twisting her neck a lot.I picked her up and her crop seemed hard so i massaged it for a while and she threw up, mostly liquid and soft short grass, it smelled a bit sour. After she had been sick she seemed to perk up a bit. Today she is more active but not chasing me for corn like the others do and she still keeps twisting her neck a lot. I am really new to this and am really worried about her. Do any of you experienced chicken lovers have any idea what might be wrong with her?