Hi, one of my chickens, a black Australorp, was sick at about 2 months old. We gave her some antibiotics which perked her up, and hasn't had any health issues since. She's about 11 months now, and a week and a half ago, we occasionally saw her nodding off during the day. We've put antibiotics and dewormer in the water and that's helped a little bit, but she's still sick. She's sluggish (sleeping most of the day and moving much slower than the others) and has trouble with depth perception, pecking the air above her food a few times before giving up. She does sometimes manage to eat and drink but she seems to have lost most of her appetite. She's also lost a considerable amount of weight, her comb is pale, and her eyes are cloudy, like she has cataracts. She has diarrhea and can still fly and find her way around the yard, her problem is measuring distance. What is this and what should we do?