Yes, you would have to lower all access points, because utilization is something shared across all access points.
You can enable "Quality Aware Arm" which would factor in channel utilization when access points choose channels. This is of course very limited in the 2.4ghz spectrum.
I would look at all my access points to see if things have lowered before doing the quality aware change. There are quite a few environments that have higher utilization but they work, so you need to baseline your utilization and user experience to determine what is the functional utilization for your network.
If your users are having problems, we can consider something else...