My 10 month old rooster's comb started turning blackish grey few months ago. I checked it few months ago, and I didn't see anything unusual and I thought it was normal for it to happen, and it will go away on it's own. It is definitely not frostbite, since I live in Hawaii, and the temperature range is usually 65-85 degress fahrenheit. He is on the top of the pecking order since few months ago, but before December last year, my other rooster's and hen's peck at his comb a lot. The white hard stuff inside the comb is surrounded by the blackish grey comb and it is close to the middle of the area where the blackish grey comb is located. He seems healthy and very active.