Well, sorry for the late reply but I was just researching the same thing and came across this. Mine has the same single comb. He's such a sweet boy I love my little guy.
I have a white leghorn that was completely white before her molt and after, she developed grayish black spots on her feathers! Now she looks exactly like my barred leghorn crosses. I thought she was full leghorn but maybe shes a cross too and it took a couple molts for her spots to show? But she...
I'm new to this forum and a little bit late to the party...however, I just wanted to say Miss Chicken I think you are an absolutely wonderful person for rescuing these chickens. We really need more people like you in the world who see chickens as a living thing and not just for egg production...