All of the chicks in this flock are 6 1/2 months old. I first noticed this one had an impaired gait in the beginning of July. I thought it was a sprain or mild injury at first, and figured it would heal with time. In the past 4 month, her condition has neither improved nor worsened. Marek's was suggested a while back, but I have been under the impression that it is a rapidly progressing disease. I cannot find anything online that gives any sort of life expectancy once symptoms begin. Is it possible that this is Marek's after all of this time? None of my other birds have any symptoms. This chick (Chicken Little) has not grown at all since July. She gets up and waddles to food & water when she wants it. She poops normal. She doesn't appear to be in any pain or distress. Other than her small size and impaired gait, I cannot identify anything else outside of the norm. She is generally segregated from the rest of the flock, which is the only thing that really bothers me about her condition. It makes me sad that she doesn't "socialize" with the other girls. Occasionally I will see one peck her when I give treats, but I haven't noticed them attacking or bullying her at any other time. She lays under the coop ramp, or under a small shelter in the run by herself all of the time. In the coop, she roosts alone while the others stay together. She is able to fly well and gets up onto the roost without difficulty. Her only problem seems to be balance. She seems to lean to her right anytime she is laying down. I have taken many pictures and videos over the months, and I'm hoping someone else has seen this and was able to treat it somehow. I do not want to put her down, but my fiancé thinks that is what should be done since she appears to be "shunned" from the flock. She doesn't seem to be suffering in any way, so I don't really know what to do. I love all of my chickens dearly and I can't stand the thought of losing one, but I don't want any of them to suffer either. Any thoughts, opinions, or suggestions would be greatly appreciated. I've looked up so many different things, and haven't found anything that seemed remarkably similar to her. Thanks!