roosters comb with bluish color

[CricketWilliams]

I have a healthy little rooster whose comb has gone from the usual bright red to one with a dark blue tinge. I have read just about everything I could find about what this could be. I've treated him for mites ( which he doesn't have ), every vitamin, even gave him a little antibiotic, with no result. I have come to the conclusion that he might have a bad heart. He was very small when born. Anyone experience this?