There is a genetic limit to how much black they will have, like you said yours are not onyx. There is also an environment link to the black. It can spread or recede(within limits) based on the clowns environment and host anemone. I have a tank that has turned all the percs I've put in it from black to orange. When I have but them in other tanks the black has returned. The process takes several months.
Judging from your pics, I would say that both have potential for the black to expand between their first two bars, but probably not between the second .