It's not easy to tell from the description what the differences are. It seems to be mainly visual effects, so I'm guessing it may be in the xfce4 and/or Thunar configurations which are held in various locations.
If you regularly use 'Backups' (Deja Dup) and know the date on which things changed visually you can check for changes around that date and revert the configuration files.
key locations to check would include these and sub directories, but there may be others.
~/.config/Thunar
~/config/xfce4
~.local/share/xfce4