Some of my fish have been pale when I bought them and brightened up later. Especially tetras and guppies. I think in some cases they were very young. One of the places I buy fish sells tetras half grown.

I don't know if your fish will develop any further white stripes. But I think it's likely the colour would brighten up. Perhaps they are young too.

Fish tend to pale from stress too.

How wide are the black bands on that "percula" clown ? true percula clowns have wider black bands and are not bright orange, they are yellower.