Not a complex but Im taking vitamin B12 as I was lacking it in my body and test showed I was headed for trouble without it. (nerve damage in legs, etc.)
Certainly I would be taking B12 and a complex wont hurt!

I take B-complex. It helps with keeping my B's up, as candida will deplete B's. But, I do find I need less of them when candida levels are down. When levels are up, I get cracks at the corners of my mouth, and taking the B's takes them away, but if candida is down, the cracks don't appear anyway (it is candida causing the cracks). However, I have been taking B's since I was a teen (decades ago), so cannot tell you how they affect my candida overall, since I had been taking them before candida.