I will get some brewers yeast.
I do feed All Flock (20% Country Companion brand) but I do mix my feed. They get cracked corn (gasp!) and wheat along with it. As a general rule, I do not share this because of how taboo it is around here.

They get free choice oyster shell and the occasional meal worms. Scraps once in a very great while.
Worming...shouldn't they be checked for worm load? I realize fecals don't always tell a complete story. I know your part of the country is different for bugs and people have to regularly de-worm, de-flea etc. Do you have a set schedule for worming? Or do you see worms, then worm them? I have seen worms on occasion, but it has never appeared to develop into a problem. I have never wormed my flock.