Sorry about your birds. Can you post any pictures? Frostbite affects the feet and toes by causing the black parts to fall off. Usually, you will see slightly swollen healthy pink tissue just above the frostbitten parts. A good treatment is to bring in the birds to a warm area, and use a warm foot bath with Epsom salts, betadine, or chlorhexidene in some water. Afterward coat the feet with either betadine, Vetericyn wound spray, or plain Neosporin ointment. Keep them inside until they are completely dry. If at all possible, bringing them inside to a basement or garage and keeping them on dry old towels may help. Toes or limbs will eventually drop off in several weeks if the are black and shriveled. With missing toes or a foot, many chickens can live okay, but if both feet are affected, most chickens would not live a good life. Please let us know how they are doing tomorrow or the next day.