Lead paint is likely because of the barns old age and the peeling, flecking paint (it falls in their water all the time).

For the first time one of my older pullets has come down with Progressive Paralysis. She seems to have walked funny all her life and is smaller than many of the others (though not unhealthy in any way other than her leg). She is in the basement because of the cold weather but she can't stay down there for too long. When it starts to warm up she will go in a crate out with the rest of the chickens. She hasn't gotten worse, but she hasn't gotten better either. She has plenty of sass, so is doing well behaviorally, but I'm afraid we'll have to put her down if she doesn't show improvement. : (