I posted pictures of my pullets recently but the more I look at this pullet I really think it is a cockeral. Larger comb, longer tail feathers, and big ol wattles. There are both Dellies hatched at the same time.
I didn't think so a few weeks ago but recently it changed so much that I feel pretty certain it is a roo. It has been getting in the other pullets' face so I thought it was trying to establish a pecking order. No crowing though.