Help! Sick Hen! Vomiting clear liquid, loose stools, lethargy, pale comb. Is drinking...

We have had wierd poops in our run for the past week. I had inspected all my hens and found a red mite, just one tiny mite, on one of my hens. I went out to dust all the hens with DE and noticed one hen was very lethargic. I picked her up to dust her and she vomited a clear liquid. Pale comb. Loose, runny, mustard, and dark orange poops. Mostly very runny. She is camped out by the waterer and was taking sips. I cleaned out the hen house, scrubbed it, put down fresh shavings and some DE in the bedding. Scrubbed all waterers and refilled adding a clove of garlic to each waterer as I read that can help give chickens a "boost". Also put a litte ACV in another waterer. Any ideas on what this could be? Sick from mites??? I only saw one mite after inspecting 8 chickens.Help greatly appreciated as I'm worried this girl doesn't have much time.