Can you leave her inside a wire dog crate (with food and water) with the other chickens inside the coop or run, so they stay familiar with her until she is able to rejoin them?
If you read this article in Merck Vet Manual, they say that quail can be affected by Mareks:
https://www.merckvetmanual.com/poultry/neoplasms-in-poultry/marek-s-disease-in-poultry
Since it is spread in feather dust and dander of the chickens, it would be difficult to control the spread I imagine.
It sounds like they had some signs of wry neck syndrome, which includes some neck twisting and walking backwards or in circles. Since it can be caused by head injury or vitamin E or thiamine deficiency, it is good to treat for that. Egg yolk(just a bit) for selenium is usually enough. I used...
Look for any mucus from her nostrils or beak, making her swallow often, any bubbles or foam in either eye, or gasping. Those all can be signs of a respiratory infection. She also could just have strider, a sound they can make when they inhale a small piece of feed. That can clear after a few...
Here is exactly how to tape the toes:
https://www.backyardchickens.com/articles/fixing-curled-toes-with-tape-picture-tutorial-and-video.75247/
Here are examples of chick slings:
https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/
Start the chick on vitamins with riboflavin or dissolve some B complex into a spoonful of water and give it some. Poultry Cell has riboflavin, Nutridrench does not, and you can give a couple of drops twice a day. Get the chick drinking and eating by dipping it’s beak often. A chick sling or...
You might want to start a new thread of your own on the emergency thread. Post it here:
https://www.backyardchickens.com/forums/emergencies-diseases-injuries-and-cures.10/post-thread
I see you had been dealing with mites in the past, and if you lose another, it would help to have your state vet...
In addition to lowering your roosts, it might also help to give him 1/2 tablet daily of human super B complex which may help his feet. Keep him on a balanced chicken feed to maintain a healthy vitamin/mineral balance for his bones. Most roosters develop red coloring on legs which indicates they...
I would not beat yourself up wondering if the bath caused her death. I only suggest that I don’t recommend soaking them when acting off. Chickens are great at acting perfectly normal even though they have something serious going on inside. Many of us have lost chickens who were acting normally...
I would clean the wound with saline or mild wound spray and apply some antibiotic ointment. Keep her separated overnight, and if it scabs and is no longer red in a day or two, try her back with her flock with supervision.
I still think he was attacked by another rooster, just due to the black scabs and the swelling. His conjunctiva (the pink tissue) in his eye look prominent possibly from past respiratory disease, and it looks like a peck mark which you have circled.