We have three chickens of roughly the same age (around 3 years old) - a buff-laced Polish rooster, a silver-laced Polish hen, and a golden comet hen. We do not keep large flocks, only a few chickens since we consider them as pets. Anyways, a few weeks ago I started to notice that our golden comet hen started to show signs of illness. At first she was more quiet than normal, so I didn't think much of it. After a few days, I started to notice that she was losing weight, and over a short period of time I notice that the weight was vanishing like magic! She started to lose weight drastically and went downhill fast. Today, around 2-3 weeks after I first notice that she was ill, she is extremely skinny, still much quieter than she should be, she's somewhat depressed (but not as bad), has kind of ruffled feathers, has a slightly pale comb and wattles, is very lethargic, and she's very weak (she stumbles sometimes, even). At first I suspected worms, but I have taken her to the vet and they could not find any traces of worms in her droppings after they examined her. The vet said that she might have a bacterial infection and they gave me some antibiotics including liquid medicine in two syringes (which she has already finished taking), and two bottles of different pills which she is still on (I have to give her a half of one pill twice a day for 10 days and a quarter of a different pill once a day for 8 days). At first, I thought she was recovering because of the antibiotics, but I realize that she is not much better than she was when I took her to the vet last Friday. If she is not recovering after she takes all of the antibiotics, I'm not sure what else I can do for her. I worry that whatever illness she might have could be contagious to our other chickens, but the others are currently showing no signs of illness. What kind of illness or disease could she have? What else can I do?