I have eight hens, Three are five years old and five are a year old. They've always had nice, dark yolks to their eggs. For the past month or so, they've started to become very light in color, like a grocery store egg. Nothing has changed about their diet. They forage on .25 acres in our backyard, get all of our kitchen scraps, and get supplemented with feed (Nutrena, I think). Unless the feed company has changed its ingredients, they are eating the same thing they've always eaten. Any ideas as to why their yolks have changed?