Vitamin E should be supplemented every few days when you give fish oil. E is depleted(fat stored) with the Omega supplement. I feed raw so give e every now and then, but most organ meat, eggs contain E naturally so I seldom give it. And it should be with mixed trochepherols.
I do give Natural C as I have a dog with allergies and C helps support the immune system and acts as a natural antihistamine. C isn't stored, but flushed so can be given daily. I'd rather give vitamins in whole foods but now and then it is hard to do...