Single combs happen more within line breeding without proper culling. You will find that instances of single combs in Wyandottes increase dramatically when purchasing birds from hatcheries. However, these are Wyandottes, not mutts. I just wouldn't consider them good breeding stock.
Thanks for posting this. You've sort of helped me figure one of mine out.
GLW = Golden Laced Wyandotte? Our little black mix hen started getting brown feathering around the neck just like that. The only difference is that she doesn't have the white striping, but rather the metallic green-tinted black of the Australorp. The lady we got this hen's hatching egg from has black Australorps, and even she thought that's what the chick was just after hatch.