I agree with cluckin_crazy, those are both reasons that chickens wouldn't lay for a period of time. I don't know where your live, or how bad the winter has been, or how long since they've actually laid. I had a spell over the winter when it was real cold and my girls really slowed down. I went from about 8-9/day to 2 from 11 girls. Someone suggested BOSS (black oil sunflower seeds) and red pepper be added to their diet. I used both and my girls started laying again and continued even after getting cold spells. They'd been down for around a month or more. I've stopped the red pepper now, because we have warmer weather now, but regularly (daily, if I have it) give them BOSS. Not sure if it was just good timing or it actually worked. Best of luck.