People make this too complicated. I've fed my chickens for years the exact same way. My chickens seem to be healthy.
Starter/grower up to around 16 weeks, then layer feed from there.
To the original poster, i offer this as a possible, standardized practice when switching feed types as your birds mature...... I always switch mine at the 16 week age or after the last bag of starter runs out. No harm, no foul. The birds are done growing by that time, and higher calcium levels...