Hmm. I have the DT-990 Pro 250 ohms. I compared the frequency profiles in Sonarworks SoundID Reference and according to their readings, the 990 32ohm has an even more extreme treble spike.

I like these headphones but I had to do a mod where I inserted 1 layer of felt and 2.5 layers of Bounty paper towel. The result is incredible. Taming the highs allows the bass to come through clearly and they're great.

Did you buy your 32 ohms used? And high frequencies can have a different meaning. My 990 250ohms spike around 9-10khz pretty sharply, but it sounds neutral-ish up to that point.

For comparison, my MDR-7506s have peaks 3-5khz and then another lesser so up around 9-10khz. So in some ways the 7506s sound brighter than the 990s.

So if you're thinking of 5-6k as high frequencies, that might explain why it's lower than you expected. These headphones get weird higher up than that, I think.