Oh dear, sounds like it could be Mareks. Sorry if I spelled it wrong. I had a run with that and I'm sorry to tell you its a long and hard process. My little silky girl never made it but ill tell you what I did and hope someone else can give you more information.
So my girl started off with me being a little worried about her for a few minor reasons but not enough for me to separate her. Until one day I come home and she's collapsed not moving in the sun. I instantly thought she had heatstroke and picked her up and rinsed her under cold water. At that point she looked awful and I didn't think shed make it but I fact, she perked up after a bit and I isolated her so I could look after her and she ended up taking a turn for the worst. I remember she was gasping for air with every breath and her leg became paralysed and there may have been mucus that I had to wipe often. Since I cant be at home all day, I had her in a little cage sitting in an aviary she she was snug and protected from the others. For a while she could drag herself around a little so I sat her in the middle, half in her bedding, half so she could reach her food and put her into the box with her bedding at night. But she got worse to the point she stayed in her bedding box all the time, couldn't move at all,was struggling to breathe awfully and couldn't eat. She didnt want to eat but everyday I went in there with a huge garbage bag around me so I didn't spread the disease to my other girls and I syringe fed her food and water with antibiotics in. It takes a while and you have to be slow, gentle and make them eat. I feed her farax which is baby formula and I mixed in crushed up mealworms and apple cider vinegar. Sometimes a bit of yogurt if she would take it being thicker. It was hard, we both fought like hell to save her and I hoped that maybe I could but unfortunately she didn't make it.
Most importantly,is the health of the rest of your flock. Try your hardest not to spread it but do your best for your sick girl.
I'm very sorry this has happened and I wish you better luck than I had but its an awful disease. And I think birds are carriers for life if they survive.
