I have a black Australorp hen, approx 8 months old. I noticed her activity had declined significantly over the past month but (as a novice chicken keeper) attritibuted it to broodiness as she would "sit" in the yard while the other hens would run around. She used to be my largest and heaviest chicken but when I finally picked her up to check her out, I noticed she has lost a lot of weight and is rather bony. Her combs and wattles are also much duller than they used to be. I have had her in isolation for the last week or so. I have given her a 7 day course of Tetracycline and de-wormed her with Piperazine (both at the suggestion of a livestock store employee), but she has had minimal improvement. Her droppings vary. Some are watery, some look dark and long (almost like cat droppings). I have been giving her a high calorie diet, her appetite seems moderate. None of my other hens seem to be affected by it. Any suggestions?