No, not necessarily. How do you know you have a B vitamin deficiency?
My hair grows very fast and it's rather shiny; it could not look that way if I was low on B vitamins. This despite the fact that my diet is very restricted because of my allergies.
I am not sure candida per se hinders vitamins B absorption drastically --there are many unproven theories in the candida department--in any case, those vitamins are present in many foods--whole grains, fish and seafood, poultry and meats, eggs, dairy products--milk and yogurt--, leafy green vegetables, beans and peas, etc.
Of course, my candida diet includes lots of brown rice, leafy greens and poultry.
That's more than enough to get all the Bs I need.