Hi, first, QUARANTINE HER! Then try a good multivitamin. Give it a chance and see if she has improvement. If she does not improve sadly it's likely Mareks disease. It's HIGHLY HIGHLY contagious and just about everywhere. It can even be spread In the wind . Was she vaccinated for Mareks after hatch? The hatcheries offer it for about a dollar per bird. If you incubate your eggs you can order the vaccine and do it yourself.I've done it BOTH ways and it's A LOT cheaper to have the hatchery do it, however still worth it if your incubating. I Might suggest any new birds brought onto your property be vaccinated BEFORE they arrive and given a few weeks to develop immunity BEFORE they touch your land or are around other current birds. I'm saying this because Mareks stays on the land for some time. However, like I said, Mareks is just about every where. That's why it's recommended to give the vaccine after hatch as babies.once they get older they could already be exposed so it wouldn't help much to vaccinate a already exposed bird.keep in mind it does NOT necessarily mean your other birds will show symptoms of MAREKS because they have been exposed. but it DOES mean, if this is in fact Mareks, they COULD and likely WILL be carriers of the disease. This is why I suggest new birds to be vaccinated. DO try the vitamins and see if she improves. if not and it is Mareks, learn as much as you can about the disease because knowledge is power. Many people have flocks with Mareks and manage quite well. learn as much as you can and it will help. I hope this helps you out a bit. Best of luck.