With a new young flock addition, she could have any number of illnesses, worms, coccidiosis, intestinal disease, or others. Lice can be found around and under the vent as well. Permethrin dust or spray used at 10 day intervals can be helpful to get rid of lice. If you can get your local vet to agree to do a fecal float on some fresh droppings, that could be very helpful. A gram stain on droppings would also be good to rule out enteritis. Gatorade or pedialyte are also good for electrolytes, and many of the chicken products have noth vitamins and electrolytes. SaveAChick, Durvet, and Rooster Booster are some of the brands that have them. I hope she continues to look better.