I have an older chicken, she could be 9-10 years old. In the past couple weeks she stopped getting in the hen house at night. I watch her try to jump in about a week ago but she didn't even get close. Every night I go out there and put her in the henhouse. Today I noticed that both of her wings are hanging low to the ground. Seems like she feels okay though, and she still wants to eat. Does anybody have any idea what could be going on?