The one leaning down in the third or fourth picture (brown with buff color around his/her neck) looks like my Brown Leghorns--which also look similar to my Welsummers. I find it hard to tell them apart, even though supposedly they have different colored ears (which I have yet to figure out.)
That's about all the help I can give you!! (first flock of chicks and they're 6-weeks old, so I'm no expert!)
-Sarah