I'm fairly new to chickens and am having a little problem. I have 6 free range hens that are supplemented with laying mash. They all have the same access to the same food. They are 3 Rhode Island, 1 Barred Rock, 1 Americauna, and 1 Australorp. The problem I am having is that one of them is laying eggs with a paper thin shell that is almost always broken before I gather. What would cause this with just one of the ladies and not the others? How do I figure out which one it is> I know it's not the Americana due to color, but all of the others are brown. And by the way, that have been laying since April and this problem has just begun in the last month. I appreciate any help with this.