Went out this morning to do the chores and found one of my chickens under the heat lamp shivering and the others has pecked on her . I brought her in and has been laying in front of a heater wrapped in towels. She does not want to eat but will drink if I bring the water to her. She tries to move her head and it starts waving around. All the other chickens seem fine. She is about 2-3 years old. Any advice?