Tubby has had bad dandruff ever since he was a little kitten, not pretty on a black cat. The vet way back then suggested premium cat food which tends to have more oils in it than the stuff you buy at the grocery store, so he's been fed Science Diet ever since - and it still hasn't made a bit of difference.

I believe they also have some oils that you can put on the dry food but I haven't really looked into those since 1986, so I can't really say much about those.

If Veronica's dandruff only shows up now and then, it very well could be the cold weather has her skin all dried out, and maybe the other kitties just naturally have more oils in their skin so it doesn't bother them.

After various other methods, I eventually gave up on Tubby's dandruff and reconciled myself to a flaky kitty. It's definitely a lot worse when I brush him.

Good luck with Veronica. Maybe they have come up with something that works better than when I was looking into it way back when.