I am currently feeding my 3 year old Golden Comets and my 7 month old Barred Rocks a Non-medicated Starter Grower 18%. With Oyster Shells separately.You mean you can feed chick starter all the way into their adult life??
One of my 3 year olds hasn't laid an egg since last May.
The 9 Chickens that are laying give me 7 to 9 eggs a day.

The reason I don't feed a 16% layers feed is because when I switched to it with my first Flock, they started to feather pick. So I won't feed less than 18% Protein. 18 to 20 percent is what works for me. GC