I have 3 red sex-link hens and I think they are getting old. These hens were given to me and I don't know how old they are. For weeks and weeks I have been finding a egg busted in the laying box. The shell is paper thin and the yolk is laying there. I give them lots of Oyster shells to keep the shells strong. I don't know what is going on. I know if the egg gets busted inside her that this is not good. Could this be old age that is causing this? I know that the hens were darker a year ago and now they have a lot of white on their feathers.