Listening fatigue is something that usually sets in a little lower in he Frequency range, as I understand it. Of course, you could absolutely be sensitive to something happening in that range... just personally haven't ever seen mention of it happening that high.
Acoustics and room set up can be a thing... as well listening volume.
You mention above "conversational volume level." This would be 60 dB, roughly, or -25dB compared to reference level. Not knowing anything more about your setup, I am curious... How loud do you actually listen?
An SPL meter, at your LP, near ear level could give you a solid result. There are phone apps that can get close enough to accurate that you don't need to go buy a special one just because.
Likewise, if you are able to set your AVR to display Relative instead of Absolute volume, as well give us your distance from speaker, that would give us a better understanding of how loud you listen. Here's a link to help explain in case you need it.
Got a tech question for Sound & Vision? Email us at AskSandV@gmail.com Q I’m confused by the volume display on my AV receiver. There are two settings to choose from, Relative and Absolute. What’s the difference, and what do they mean? —Scott Oakley / via e-mail A The relative volume display on...
www.soundandvision.com
On a slightly different note, you could also try using EQ (if built in to your AVR) to see if adjusting downwards the frequencies in question help... just as an experiment... try -3dB at the two nearest frequencies to your problem area. Also experiment with the area I mentioned around 2000Hz.
Next, do you have the speakers aimed directly at you? Are they perpendicular to the front wall? Changing the angle a little can help, potentially.
Room acoustics can also play a roll in that lots of refection can seemingly promote those higher frequencies. If you stand in a quiet room and clap your hands, do you hear an echo? Possibly damping your room with some absorptive material can help. Carpet or a good area rug on the floor; artwork, knick-knacks, bookshelves with books; comfy furnishings; etc... all of these can help absorb and diffuse the soundwaves that are possibly irritating you.
Beyond that, I have experienced one set of speaker that caused me listening fatigue. It was not fun. Some of the advice I just mentioned was given to me at the time I was discussing it.
Hope this might help!
Cheers
EDIT: A little refresher reading shows some differing FR points for Fatigue, with one going a full 2 Octaves from 2000-8000Hz. Others show ~5500Hz as the upper range. Many comments are also made about SPL as a prime contributing factor.