I did something similar a while ago, but I think it was only b12 or something, not all the Bs. I didn't notice too much of a difference at the time, but I'll dig at it again after seeing your post. I've also came to the same conclusion regarding sleep. But for me it affects everything, not only speech. I can get by with 7-8 hours, but with 9 I feel way more refreshed and sharper.