I have three healthy, beautiful chickens - a black copper maran, an andalusian, and a mix maran/andalusian. My copper maran laid one egg on Sept. 12 when she was 21 weeks old. It was a gorgeous, deep, chocolate brown egg. Unfortunately, it is the only egg she has laid. One of the other chickens started laying about a month later. It has now been two months since and she is 31 weeks old and she has yet to lay another egg. She has a bright, red comb and is very active. She seems totally healthy. I am feeding her layer feed with extra calcium. Should I be concerned?