You switch to an all flock and add free choice calcium (such as oyster shell) on the side for the laying birds. You can feed everyone all flock, from chicks to roos to 7 year old hens.
My birds were on DuMor for some time - I was reccommend Nature Wise's meatbird crumble by a breeder. It has dramatically increased their feather health!
They need lots of oyster shell on it of course, but the shiny feathers and happy birds make up for the added cost :p