well, based on that info I would say you need to add oyster shell/crushed egg shells free choice. My piggy hens will always eat the chick starter if available. If she is eating too much chick feed than she doesn't have enough calcium. It won't hurt to add, and hopefully it will fix the problem...
Molts can happen at different ages, I have some two year old hens that have never had a full blown molt, a 13 week old that is currently having a heavy juvenile molt, and one who molts once a year like clockwork. Are you providing extra calcium free choice? And if the covering was brown, it...
aart is right, not always so straight forward, should have asked for more info! Shell less eggs can also come from new layers just getting started, older hens, hens with a problem in the shell gland, recent stress (predator attack, moved the coop, etc), and many other reasons that I probably...