Age the age of the actor is less of a problem than his look. The Actors is already 20 he just looks like he was still a teen and than will probably not change any time soon.
In general most of the actors on that show (except for Teagan Croft/Raven) are older than their characters a probably supposed to be: Brenton Thwaites/Robin is 29, Anna Diop/Starfire is 30 and Ryan Potter/Beats Boy is 23.