Where did you get them? If they came from a hatchery, to a feed store, and you got them from there, I'm guessing this "different" chick accidentally got mixed into the sex link bin. USUALLY, sex linked chicks from a hatchery look very much like each other.
Well I'll have to post a new pick in a few weeks! We will wait and see. I like chickens that are a tad bit off of the others. Some of them turn out super pretty