I think the black one may be a pullet, i cant see much of a comb. the splash (who is very very beautiful by the way) is hard to tell because its bearded. I always look at my chicks waddles and combs.
I have had bad luck with my chicks and now I only buy pullets. It was to heart breaking! And it's not easy having to keep rehoming roos. I have had so many roos. 4/4 in one lot I bought
I have 1 dominant roo. He is the only one who crows during the day. In the morning they will all crow.
When I have a roo who starts crowing he gets brought inside of a night/morning and put into our rooster box. Because we were doing this, another chick would step up and if ready, they would start to crow. S in answer to your question, yes! Removing the dominant roo can give opportunity for another one to crow.
Good luck I hope you only end up with 1 roo as willow is divine!