Letting the chicks out for supervised free ranging or time in a chicken tractor really improved the feather quality on mine last year. The fresh green food and bugs just gave them nutrition that wasn't in the crumbles.
I thought the feathering on the chicks I raised last year, didn't look as good as they had in the past, before the feed industry started to go with all vegetarian feed ingredients. I noticed a difference and got them out on pasture as early as I could. It really helped them.
Green feed also makes chickens healthier and pastured chickens produce eggs that are healthier for you to eat.
I put them out in a tractor as much as the weather allows. It's been pretty rotten weather around here the past couple of weeks, and these chicks are just now getting feathered out pretty good. The temps haven't been warm enough to let them stay out for too long. Every day that they don't get to go outside, my son (3yrs old) and I pick grass and weeds for them, and catch crickets too (we've got 1000's of them behind my barn). I know it will be MUCH better when they can go outside permanently...but by then the bugs and grass will be gone! These poor darlings just don't have much luck until next spring. This Michigan weather really stinks!