I have some BO's, RIR's, one real Ameraucana, and 3 EE's. I have noticed that their colors aren't as vibrant as they were in the spring. Their combs and feathers seem faded. Is this "normal" for winter? Do they NEED vitamins to bring out their color? They are all in good health otherwise. They are still laying (even though it has slowed), eating great, I would say content birds.