https://www.amazon.com/Nutri-Drench-Poultry-Solution-FL-OZ/dp/B00GSOD8KGShe is probably sick. Use nutri drench for extra nutrients. Pick her up and place her next to a small feeder and waterer which are close together so she can eat and drink just by stretching her neck. I don't know what is...
I'm not sure. Their tails try to convince you that they are roos. Their comb size may mean they are roos too, but it might just be the breed. I have a hen with a LARGE tail and when I say large, I mean it.
Dust baths are supposed to suffocate mites. If you want to add extra stuff, add diatomaceous dirt (a chemical, so you might not like it), lavender, or some other herbs. Ashes from fires are also good for them.