It's been two days since our last soft egg shell. For three days I've been giving them a bowl of milk each day, and for two days I've been mixing oyster shell into their food (I always have it out, but I'm not sure they eat it). I know I just started doing these things, but I swear we can tell a difference in all of the eggs and are getting really thick shells now. Maybe it's a coincidence, but maybe the calcium really could help that quickly. I've also seen no more evidence of egg eating. Hopefully the entire problem for both of these issues was a lack of calcium and has been resolved. Keeping my fingers crossed!