Chicken that old still need to have a starter grower ,then grower finisher,cracked corn maybe little to heavy on them ,they may not be able to digest ,cracked cor usually is feed for 7months and up ,wish u best :)
I will check it out watter feeder made from 5 gallon bucket after paint ,any restaurant have plenty of them I'm sure they will give out some for free.Then frizz the water in will stay cool for almost 5 hours slowly melting,(need also good size freezer for that)