Age has nothing to do with maturity (as I tell my teenage son

). Seriously though, clowns in the wild will stay as juveniles indefinitely if the conditions are not right for them to sexually mature.
Trust me - that maroon is a juvenile, and the other two clowns probably are as well. Any two of those clowns pair up, and the third will be harassed to death. That's just the way it is. This forum is loaded with threads about "my clowns got along together for years, and then two started spawning and now they are fighting all the time."
Additionally, you have to understand that captive-raised clowns are raised in very different conditions than what they experience in the wild. They start their lives in very crowded conditions with tons of clowns all around them. They are probably much more "accustomed" to being with other clowns - and other strange clowns - than wild caught clowns are. Once they sexually mature, however, Mother Nature reasserts herself.