My 5 22 week old hens start laying about 3 weeks ago. I get 4-5 smallish brown eggs every day. Yesterday and today 1 has had white spots on the shell the color of the ground oyster shells I've been giving them. They're finishing off their pullet grower (with the oyster shells on the side) and I'm transitioning them to the layer feed (Layena). Is one hen just eating too much of the oyster shells? Should I stop providing them with the oyster shells once I switch to the layer feed full time?