Ear fatigue or just sibilant?

I have a SHP9500. I’ve been on these for a week. One thing I noticed though, when I’m listening for at least an hour, the inside of my ears starts to hurt. I had to rest for awhile because of it. But my ear just hurts afterwards, to the point I wanted to swab it with q-tips. It’s like the effect of listening to IEMs for a while. I don’t even blast it to full gain. I just play it around 30-40/100 only. I also didn’t EQ it. Just enough to hear the details of a song.

Am I getting this pain because listening to at least an hour could really cause fatigue or this is because SHP9500s are just sibilant and I am treble sensitive? Or I could have ear problems? Lol

I actually wanted to get the DT990 later, considering its build and clarity. I like the details and clarity that SHP9500 outputs. But I’m not really sure if I’ll enjoy the DT990 with my current experience with the SHP9500.

Also, in case I am sensitive to treble, which sound signatures or headphone brands will be better?