I have a young Marans girl that has been like that since the day she way born.
I would venture to say just her. Not sure if I would breed it forward it it doesn't show improvement with age. Could be genetic and definitely isn't aesthetically pleasing, as far as breeding goes.
You are right though just because something CAN mean illness doesn't mean it is. The more birds I have, the more things I see out of the ordinary. How cool is that this guy who got a rooster from me had a red sex link broody hen successfully hatch and raise chicks!
Could be a sign of her place in the pecking order. Have you checked for red roost mites, northern fowl mites or lice? Do you see any irritation around her vent area. Like redness?
Your birds are beautiful!
Cocci is always present. It's only an issue when there is an overgrowth sometimes brought on by climate. Treatments for cocci ONLY slow the growth and do NOT actually kill it. Did your birds need to be wormed or you just did it? Did you treat for the right worms? Not all meds treat all worms. (and especially if you are one who worms with DE). Not saying I think that's it, just sharing info.
