Hi - I have four female khaki campbells that were born in May. I got the first egg Labor Day weekend, and they were starting to lay pretty regularly (3/day). But in the past 24 hours I have gotten one regular egg and 3 eggs without shells. Someone told me that means that they are not getting enough calcium. After the first one, I thought that it was one duck was still figuring out the whole egg-laying thing, but two more means (I assume) that more than one duck is affected. The other factor is that it has just gotten very cold (Massachusetts). Could that be why? I am a newbie to poultry-raising. Thanks for any advice!