Hi there, hope you are enjoying BYC!
No, while some flocks do have preference to certain feed formulations or even pellet size.. the first poster hit the issue dead on, without any doubt.
TOO many HIGH value treats are being mixed in with the standard ration which is lower in fat than seed and more balanced than grains.. like corn which are often high energy content but don't have the added vitamins and minerals.
Remove everything BUT the pellets.. make sure their feeder is raised level with their backs to help reduce waste.. and offer the other things ONLY as a special treat coming from YOU/family personally.. and at NO more than 10% of their total daily intake.. Otherwise all bets are off as long as you continue with your current feeding practice. Great job describing, btw.. I didn't catch what type of feeder you are using.
Feeding pellets is like offering broccoli next to seed and corn is more like chips if you will.. lots of protest.. it will take a minute or two for your flock to adjust as they are creatures of habit.. But they'll quickly get with the new routine. And I PROMISE you won't regret making the change.. it will pay off long term in the health and well being of your flock which also ultimately will benefit your whole family!
Avian nutrition.. is kinda my obsession.. I've literally spent hundreds of hours on it..
My personal flock is more wasteful of pellets than crumble. But they also love when I wet it into a mash.. which is how some folks reduce waste.. as another suggestion.. but reducing access to high reward feed stuffs is going to be a major key for you, especially noting your location/mild weather, (city size range minimal ranging?), etc.