They’re still juveniles, if they’ve been together for less than a year and they’re both under 2” they’re not really ‘paired’ yet. If the seller is willing, it’s no trauma to separate them at this stage in development and replace with a fish you like better. Most LFS will take a trade in, one clown for another.
a word of caution, longfin clowns are like betta fish in that they cannot handle strong currents. So if you have strong currents in your tank, turn them down because the clown’s swimming ability is impacted by the over sizing of the fins. Lost my first longfin to high flow