Similar concern on this end. I have 4 hens (3 RIR's and 1 Plymouth Rock). My "girls" are mature: 3+ years old. I too have noticed their brown eggs getting lighter this summer (+ egg production is down). Getting about 1 egg a day for the past few weeks, when usually it was 2-3. Hmmm, is this normal or should I be concerned? Everything else seems fine. No change in their routine or diet (I feed a "complete formula" poultry layer feed, w/ oyster shell). They have access to clean water all day. Free-range within a fenced area all day.