Yes. Although these vitamins are common nouns, they are often used as proper nouns. TECHNICALLY, none of them should be capitalized. However, some of them have become synonymous with certain proper nouns.
Therefore, it is best to capitalize them, because that is what readers will expect.
Do, however, be consistent. Capitalize both words. Rose Hips, not Rose hips. Or, if you want to be perfectly correct, capitalize NONE of them. Be prepared to be "corrected" if you do.