In terms of vitamin deficiency, I'm actually most suspicious of vitamin B12. Both my maternal grandmother and my mother have low levels and get B12 injections regularly. (My mom is currently 60.) I once asked my psychiatrist to have my B12 checked, but I don't think it actually has been.

I suggest trying emergen-c or your local generic version. It's mostly marketed for the vitamin C megadose, but 416% of the recommended minimum of B12 isn't insignificant. The generic I use has an odd taste when prepared according to the directions, but is good when mixed with a sweet drink like kool-aide.