one of my black alstrop 6 mo old hens died today. This morning she was sitting in the yard, she got up when I walked up to her and looked fine except she was opening her mouth and sticking her head up. Checking her around noon and she was in the hen house doing the same thing. Her weight was the same as the other birds and her eyes and color was good. just went to check on her at 3:00 pm and she had died.??? feeling her crop it was flat not bound. Any idea what happened to her?