A good way to get B vitamins is to eat beef liver, or to take nutritional yeast (not brewer's yeast!!!). This will give you a definite stable and natural way of taking B complex and should be fine.

I think B complex taken in vitamin form can sometimes cause issues, as nothing is going to be exactly how you need it and may disrupt some ther vitamin in the process. So you might find having it in food form of either eating liver (or taking it in dessicated liver tablets instead of that is easier), or the nutritional yeast ...