Are they acting normal?
Sometimes fish will loose a little color.Some fish even change color at night.
But its hard to say about the clowns,without more info.
I hadve a clown that was chased around by the other clown for a month or two. He was pale. Put him in the QT and now he regained his color and gaining some weight back and doing great.
My tomato clowns turn whitish at night. It's normal for clowns, I think. I've had one of the clowns for 2 1/2 years, and the other one for about 6 months, and they are totally healthy.