About 2.5 days ago, I noticed that my chicken can barely walk, and she doesn't want to eat. She is a bantam golden laced cochin about 1.55 years old, and lives in pen. I started giving her antibiotics since 2 days ago, at a dosage of 125mg amoxicillin every 12 hours. She ate very little without help about 12 hours ago, but she doesn't want to eat again on her own. Also, her head is tilting 45 degress +/- 10 degress towards the left side, and she is staying at the same spot for several hours, and can only walk for 2-3 seconds if she feels scared. I didn't see any visible signs of internal or external injury around her neck and head. She ate the same food as my other chickens, but all of those chickens seems healthy. I am currently giving her ensure plus, water and vitamins that I am giving to my parrots. What is her problem, and what should I do?