Is this a normal amount for 19 chickens to consume? I think they may even eat more if I put it out....... Should you feed free choice? These are free range birds although they seem to prefer the crumbles to scurraging for their own meals!
You might have other critters getting their feed, either wild birds or mice. However, it doesn't sound unreasonable, I give my Marans about 3 pounds a day and there are only 7 birds in that pen. They don't eat it all but they do clean most of it up.