One of my girls (I don't know which one) has laid an egg that has a very soft shell. It has not burst, but is malleable and feels kinda sandpapery. Its honestly pretty gross, but I don't know what to do with it. The chickens are about 9 months old and are all Australorps. We have had a cold winter so maybe that has had something to do with it? My first guess is a calcium deficiency. Every morning we give them 1 scoop of Purina chicken feed and whatever left overs we had from the night before. If there is anything else I should do or be feeding them please let me know. Thanks!