I've got 7 ISA browns about 4-5 weeks old. Just in the past day or so seems like they've started eating more. They do waste a little scratching at it. I usually feed them in the morning and by 3-4 they're out. Should I feed them just a little more or fill it back up? They're in a homemade pen right now. And at what age do u start feeding chickens layer crumbles? Still a newbie.