Is this normal? Heard it’s called smut?

[bumblychicken]

Wasn’t exactly sure where to put this but I’ve seen this on another one of my buff orpington pullets but on that one’s tail feathers. The one pictured is on the wing.

I think it’s what people refer to as smut but wanted another opinion(s)

 

[Wyorp Rock]

I've heard it called smudging or smutting. It's color leakage.
As the bird gets older and goes through more molts you may notice more leakage or stippling/coloring of the feathers.