I’d say overtime you could breed the mutants out. But it would be much easier to just go back and figure out which parent(s) passed the gene down.
And I mean… unless you’re seeing a ton of them I wouldn’t make a fuss about it. Especially for a home breeder.
I’ve had mutants from some of the top breeders even. I’d say if he’s happy with most of the progeny then no harm.