We have a hen laying soft eggs on a weekly basis. This hen is one of three that we got as chicks, and are our first chicken experience. I've read it can be caused by stress, but we have an enclosed chicken run with no predator access that I know of, and no changes to location, other animals, etc. I also provide ground oyster shells in a dish adjacent to their feeder. We don't have this problem with either of the other two hens. What else could be causing soft eggs?