I have 2 female Pekin mix ducks, one female has quit laying a while ago but the little female (I call her little momma) still lays an egg EVERY day. I have noticed that her eggs are not as strong/thick shelled as they used to be. They free range all day long and when we lock them up at night we feed them a chicken layer feed. (supposedly acceptable for ducks also. purchased from Farm and Fleet) What should I get to help supplement our ducks feed? Or is there a proven all in one product that I should get?