clownfish won't start mating after 12~24months old. cuz they need to be physical muture before they change their sex.
I doubt they r mating since you said theres tiny one that doesn't even have all its stripes yet.
if they r the same size, you might see them fighting in the future, cuz they need to fight out who is gonna be the female, (if one is bigger, they will probably forget the fighting and the bigger one will become female)
then they will bond together.
if water condition and other requirements r good, then they will start mating and lay eggs.
so +2 its natural that they twitch something.
here is a really good article for pairing clowns and how they mate.
Forming pair bonds in clownfish - a knol by Anonymous
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