My best layer has been laying all winter, most days. She used to lay brown eggs but they have gradually been getting lighter in colour. They are almost white now. My other hen hardly laid any eggs over winter and her eggs are very brown. They both eat the same diet. The brown layer has 'tanned' looking yellow-brown legs and the white layer now has pinky-white legs. I was wondering if something is being 'used up' from the body of the white layer. I am interested in what makes the colour of the shell, and if the hen needs something to improve her shells. They are about 2.5 years old and in good health.