They best thing is to get them on good layer which it sounds like they are on and fresh water. Next time you're in your farm supply store, look for a bag of probiotics for their water, and some Poultry Cell also for their water. They could have been suffering from vitamin deficiencies from before you took over, and the probiotics will help their gut and crop. You can give them sugarfree yogurt if you have any, or apple cider vinegar w/ the mother 1 Tablespoon per gallon of water a couple of times a week.
