I'm new to raising chickens. I have 4 Wyandotte hens, no roosters, that are about 15 weeks old. They are big girls and look fully grown. They are eating pellets now. One of the four just stopped coming out of the coop yesterday. When my husband finally got her to come out today, she wouldn't stand up. She was stretching her neck to eat and would just lie down wherever he placed her. I'm not sure what to do. Please help!