Aaaaand the crow has confirmed it. Over the last week or 2, the "girl" on the right turned into full blow cockerel. The chest is black, the shiny hackle feathers came out and the pretty iridescent black saddle/sickle feathers have popped out from under all the other feathers on the tail. I contacted the person where I bought it and it turns out, this Partridge Rock comes from show lines (Horstman?) and it explains why it's taken so long for him to properly feather out. He's turning into a beauty except for the fact that I don't want a chicken that won't give me an egg. In hindsight, it was clear. I should have known but I wanted a girl so bad, I told myself that it was mixed with leghorn and that's why it had a bigger comb that the other.
So Metella, if you read this, I change my vote from pullet to roo on yours as well.