Treating mildew?

[ॐ]

Hey everyone,

I just noticed my salvia plant has gotten infected with mildew (at least that's what I think it is).
It's not too bad (yet), just some small fuzzy white growth on a couple of leaves, but I think I should act quickly to treat this before it gets worse, especially now that the temperatures are dropping and the plant is more delicate. What would be a good treatment method that wouldn't harm the plant?

Thanks!