It’s just you. 
Seriously, every time a new build is released someone or many find that either the SQ has improved or (more frequently) that it has gotten worse.
Dunno, here’s a list of the changes/fixes in the Build 831. Unless you have new Audeze headphones or are running S2 Gen software on a Sonos device, do you see anything that might affect (one way or the other) SQ?