My dad's RIR are about 1 1/2 years old. When they were first laying, they layed very dark brown eggs (for a RIR). This past winter my dad decided to switch them from Purina Layena feed to a 16% calf grower feed that is mixed by our feed store (has soy meal, distillery grain, cracked corn, oats, etc). The birds are now full-time free rangers, when before they were never let out of their run. Their eggs got a little lighter, but they were also about a year old. I just figured they were at the end of their 'cycle', and the eggs would darken. Not only have they not gotten darker, most of them are almost white now. What would cause this? Diet, illness?? I'm seriously at a loss.