I was brought up with the rule of thumb that 2 weks medicated starter mash, then switched to non medicated starter crumles for additional 6 weeks. The starter is really about a higher protien percentage to get them going strong. After the 8 weeksm then switch to a grower ration with protienn around 17 percent for 12 more weeks, then switch over to the layer pellets.
I prefer pellets as soon as they are old enough to eat them, since the ones that go to the gound or floor will be picked up. Not the case with crumbles, hence more waste.
This december I tried something different. i got 13 Pekin ducks from metzner farms, and 25 RIR from Ideal. Waterfowl should not have medicated feed or suppliments in water so i fer both chicken and ducks a Turkey Starter mash, non medicated. After 3 weeks switched tio the crumbl form with same formula. At five weeks the ducks (which weigh in around 3 to 4 pounds) now eat pellets, and the chicks on crumbles.
I collect greens from a grocery store and chop them in the food processor daily. In addition I feed them organic juice pulp from a health bar.
Seems to be working great.