I got home today and noticed quite a few jet black chicken poop around the pen... I watched for awhile to see who was doing it and it was one of my girls.. as far as I could tell it was only her.. she seems physically fine, she has had a really bad twitch for a few months with her head, she always shakes it like she has a fly on her head, I have no idea if that could be part of the problem but she's the only one with a twitch, she's only 15 weeks old.. I'm so worried because I don't now whats wrong or how to fix it! please help! has anyone seen this before?