My one BR hen is now about 1 1/2yrs. She molted in the winter and after that started laying a nice big egg. Recently I have notice her eggs are getting smaller. In the winter I had them on 22% layer as they were not eating much. Since introducing my two new pullets about 4 weeks ago they have all been on 18% start and grow with oyster shell available at all times. Why are her eggs smaller? Is it the feed? The heat?