Rocky, for Ko, yes, warm clean water and 1 tsp of AQ salt for him with as many water changes as you can do. For your girl, I'd have to see a close up pic of her. Some bettas have natural gold coloring. With velvet, even though it's a gold dust, you can still see individual spots like parasites. To be, it looks more like a fish has been coated in corn crumbs than gold dust. If you can get a good pic, that would help. For now, try to keep her separate from the others and cover her with a towel or something so she stays dark.