To put them into their 2nd year of laying, then they get rid of them.
I have one 6 year old hen still laying. My other 6 year old hen quit 2 years ago. ( but she went broody last year and raised babies). Production starts decreasing each year after the 2nd year.
I'm sorry you had to learn...
They just haven't started yet. They will. I have some almost done with their molt, some mid molt, and some that haven't started yet.
It certainly wouldn't hurt to give them high protein treats now. Oatmeal doesn't have much protein, so I'd substitute something that does like mealworms, meat...