A lot of different feeds and opinions, probably all will work. I feed mine 20% started for about 10 weeks then switch to 15/16% grower/finisher till they start to lay then Layer. Its according to what breed as to when they will start laying---some sooner than others----about 5 months to 7 months.
What breeds have you got? Breed factors into maturity rate and the expected onset of production -- there is some variance even within breed, so the general window for eggs is "somewhere between 20-35 weeks" with a +/- of 2 weeks to either side. As to feeding - everyone has their way of doing it. Some, myself included, use an all-life-stages approach to feeding using feed that is appropriate for all ages and stages such as Flock Raiser, All-Flock, grower ration, etc and feed that from the first to last day a bird is in the flock, offering calcium in a separate container to be taken as needed by those birds actively laying eggs. Others opt for the starter - grower - layer approach. The transition point for these feeds can vary from brand to brand so it is often best to consult the packaging for the feed line you are using as different producers formulate each "stage" a bit differently. You can also opt for using starter and feeding it to the point of lay then going to layer, starting with grower and going to the point of lay transition or any other number of potential options.
