Sounds like you are doing OK. A general rule of thumb is to not give them more than they can clean up in 10 to 20 minutes. Their feed is a balanced diet and chickens need a balanced diet, like you, me and everyone else. Too much of a good thing is not a good thing if it throws their system out of balance.
Do I follow that rule myself? Not really. When I can something or have waste from the garden they can wind up with more than they can finish immediately. But I don’t give them large quantities of the same thing day after day but mix it up quite a bit. That way they can splurge occasionally without it really affecting their overall health.