Audio quality changes when my phone screen locks

[Jpkenneys]

Over the past year I have noticed a significant drop in audio quality when my phone screen is off. If Spotify is open the sound is crisp and sounds good. When my screen switches off there is an instant drop in treble and the music sounds muffled. I've tried several things like reinstalling the app, turning off the widgets, gone through all the audio settings on the app and my headphones. This issue happens with several different headphones I've tried as well.

I'm using a Samsung galaxy s21.