I have 2 barred rocks and 2 red sex links. All 4 are almost 16 weeks old. The 2 sex links and 1 of the barred rocks look the same, maturity wise, in the growth of the combs and wattles. The other rock's comb and wattles are visible but not growing at all. She is otherwise in great shape. She is as big as her sisters. She shows no signs of being ill. Just no development of the comb/wattles. What gives?