Once my pullets hit 16 weeks they get laying pellets. The only other things they ever get are plant matter from the garden and insects. No scratch, no corn, no oyster shell, just pellets.

we used to feed our chickens (we got rid of them due to neighbor's dog eating them) laying pellets, oyster shell and cracked corn, ocasionally the scratch when it was on sale, whether they were laying or not, if one is laying it needs it and you really cannot single out one chicken and feed it something different.
The laying pellets didn't hurt the others at all, in fact it seemed as though they had shorter times of not laying with the pellets.
Now I try to feed the pellets to my ducks but the goats seem to like them better. (I doubt they will ever lay an egg though) ;)

Layer feed is formulated to produce the most eggs at the least cost. It shouldnt hurt to feed it to alll poultry all of the time. Young birds do best fed starter grower until lay begins then gradually make the switch.
I never feed layer as I use my birds for breeding. I feed a game bird conditioner for well started young birds and to all after hatching season is over. Beginning a month before saving eggs they are switched to game bird breeder pellets to achieve the best eggs and youngsters.
Many feed turkey grower to their birds.
Some corn or mixed scratch grains is fine used as a treat in the evening. A container of shell and grit is fine but the layer rations have adequate calcium for most flocks.