Some people cannot activate pyridoxine to pyridoxal in the body.
So the pyridoxine builds up.

The same goes for folic acid. The error for folate is called MTHFR polymorphism. There is considerable folic acid in foods today in the US. Fortified foods. And there are some papers out there now, describing how synthetic folic acid my block the activity of natural folates at the blood brain barrier. Karsten sent me this paper about that:
http://www.ajcn.org/content/87/3/517.long

Too much Vit C can cause increased acid in the blood, but this is temporary for the most part. Using an Ester C avoids that.
But Vit C is necessary for good gums and oral mucosa health.

People can all vary considerably metabolically depending on their genetics.

If vitamins bother you in some way, I'd take that as a sign to not use any. You can get your magnesium by soaking in epsom salts or using a lotion containing magnesium.

Did your doctor tell you the numbers for the B12? or just "normal"? I'd get the numbers if you don't have them. Very low levels show up "normal" on the old lab ranges in US still.
You should be at 400 at least, and preferably higher.