Yes, European breeds makes a difference, however I am picking up a Legbar in one due to the cresting...Looks to be a Cream Crested Legbar in the back by the fence.
The middle black bird, if in America, looks to be an Olive Egger mix, possibly Marans.
Then the two amber eyed birds I would suggest are a Black Marans and Cuckoo Marans.
It looks as if you've got someone's Olive Egger flock.
What color of eggs are you getting? If it's plain jane brown or white, then they are likely just barnyard mixes.
Legbars lay blue-green eggs, so that may be from your Legbar mix. The Marans (if they are so) *should* lay a nice dark brown...varies with lines as to how dark. Often it comes out looking like a terra cotta garden pot color, sometimes with spots.