I second your assessment! I have black Australorp pullets and a cockerel and the white tipped wings/feathers are just as it sounds, a little bit of white on a few wing feather. Other than that they are solid black with a glossy, green sheen. :) They look healthy though!
Black australorp - Page 2
I agree with your assessment. The legs still look white to me rather than yellow and the pattern looks like the looser barring of the Cuckoo Marans rather than the tighter barring of the Barred Rocks. The larger comb development of the three on the left has me thinking cockerel on them. The two on the right with the smaller combs are pullets.