My 5 girls are 16 months old today, I got them at 2 days old. I've never treated them for worms, nor illness. Never gave them vitamins or electrolytes. Last week we had a 4 day heat wave, and I got 32 eggs, Sunday through Saturday.The fresh vegetables are fine for the most part, but grains and beans both contain anti-nutrients (chemicals that prevent nutrient absorption and/or actually do damage). Fermenting breaks down a lot of those chemicals into more tolerable and/or beneficial ones. Eating fermented foods is actually good for humans as well.
Although this article is about human nutrition, it should offer you some insight on why anti-nutrients are a problem and what can be done to help yours and your flock's nutrition.
PS- If you try it, you might be surprised how much your birds like it. Mine dove in right away when I first made FF.
My girls love their pellets. I open the coop at 5 a.m. year round. As soon as I turn on the light the girls make a beeline to the feeder or nest box.
I buy the freshest feed with prebiotics and probiotics in the formula. I buy one bag at a time, even if its on sale, store in my house till I need to refill my feeder. It's so nice to refill the feeder once a week. GC