Welcome to the forum, I’ve not hand raised a baby quaker either. I am sure your breeder that you got them from would have answers. Though you should probably keep feeding until you see them eating on their own. Hope you can get more answers from the breeder
I have read that you should keep hand feeding them until they reject the feedings. So make adult bird food available in the cage and offer bits by hand, but keep spoon or syringe feeding until he refuses it because he’s eating enough in his own.