Small doesn't always mean juvenile. I have seen a lot of nigripes that were small <1.5 and all have had black belly fins. Small fish can be old, they just aren't the dominant fish in their anemone, so they don't grow.
In the early 90's a pairs of leukocranos spawned at the Birch Aquarium in San Diego. At least one batch of babies was raised. I was lucky enough to see the tank of babies myself. The parents had not bred true. The markings on the babies ranged from two complete side bars only to one skunk stripe only and everything in between. Only about 25% of the babies had "classic" white cap markings. The failure to breed true would mean it is not a species.
Later (or maybe before) a Chrysopterus x sandaracinos(orange skunk) pair was discovered with eggs in the New Guinea/Soloman Islands area, where you find white caps.
From what I understand, it is not uncommon to find white caps paired with chrysopterus or sandaracinos clowns in the wild.
As for the nigripes, I have seen some in my area lately, so somebody is bringing them in right now. Good Luck