My blue cochins. When this picture was taken she was eating "Grower"
"When do I switch from Grower to Layer?"
I feed my babies "Starter" until about 8 weeks.
Then I switch to "Grower Mash" until they are fully "feathered out" about 20 weeks.
Next I switch them over to "Layer Pellet" I do not use "Layer crumble or mash".
I also mix in some:
Black Sunflower Seeds
GameBird Pellets (higher in protein)
There are lots of ways to feed your birds. This is just one suggestion.