The top one could also be a brown leghorn. I have two that look like that. My welsummer chick is very similar as well, but is more reddish brown. The leghorns are darker brown. I'm not positive though. I'm new to all these different chicks too!
Editing this post to death. LOL.
The brown is definitely either a silver duckwing oe or Easter egger bantam. My money's on silver duckwing. I'll try to post pics of mine later; they were identical.
Does the black have feathered legs? If not, I'd say black Japanese bantam. If so, probably black Cochin.