Aaa, I see!
When searching for the buildup, I found that the room had a bump at around 450-500 Hz range, which I could reduce. That also removed most of the buildup.
The same bump is visible also in the overhead. But as I already have a 350 Hz cut there, I did not touch it further.
The snare was fine, with very little above 200 Hz, so I did not change that.
The base also has a lot above 200 Hz, but reducing that was not good for the tone of the base, especially when the base was playing without the guitars. so I decided to keep it.
Two of the rhythm guitars also had a lot in the 200-500 region, so I took out 1-2 db at 350Hz on both. that also increased clarity in that range.
But in total, reducing the room had the biggest effect. I took out about 5 dB at 450 Hz. I made the high pass steeper at 24 db/octave, up from 12 db/octave, with the frequency set at 220Hz.
So thanks once again for pointing this out to me! It really helps me improve my mixing!