I purchased five chicks from a good breeder. They were one week old when I got them. They are now 6 weeks old. One of the chicks just started having trouble walking. She is dragging her one leg/foot behind her. If I pinch her toe, she yanks it so she feels the foot. She was in the brooder with four other chicks and all are fine. I have 28 birds on the property and all are acting fine. I have vitamins to this chick and she is very perked up. Eating and drinking if I help her get to it. Is it meraks or something else? If it were Mareks then wouldn't some other chicks or chickens have symptoms also? If it were Mareks then would she be able to yank her leg when I pinch her toe? PLEASE HELP!