Looks completely normal to me, all of your higher channel utilization channels are 2.4Ghz and the majority of your clients are on 5GHz so they are not being impacted by this. You can get close to 30% channel utilization on 2.4Ghz without any clients just due to beacons and management frames, it propogates further and there are only three non-overlapping channels.
If you haven't already, try enabling broadcast filters and trimming your beacon and basic TX rates on 2.4Ghz and do a before/after.