If these birds are 7 mos. shouldn't they be laying by now? If either of them is a hen? I have CM that began to lay in cold November and have been laying pretty good. If you suspect a hen and your other hens are laying and "she" isn't then, she either late or a roo, right?
Though I too would think the black cochin is a hen. There are many things that can affect a hens laying or not.
As for the non- crowing roo, seperate him for a time and if he's a roo, he'll start to crow. Nothing brings out a roos horns than when he's been seperated for a time. Course you could start having fights like Eric and Nick. They fight til there's blood and even through a screen/poultry wire door.