Wipe her mouth and throat gently with a Q tip. If she has gapeworm, you will retrieve one or a few very thin long red worms, about 1" or so. Gapeworm is quite unusual, but quite serious if it occurs. This really sounds to me more like they need good nutrition, attention, a clean place to live, lots of space, etc. Some chickens who get a rough start are going to need longer to recover than others. I would be careful not to overdo anything, whether it is vitamins, greens, electrolytes, etc. They do need layer or another calcium source such as oyster shell if they are laying, for good shells. Most chicken feeds are vegetarian and chickens or course are omnivores, so another good supplement is most any animal protein. Many people farm mealworms these days for this purpose. A few house leftovers or an occasional can of canned mackerel are other sources.