There's a bug with the new version of Discogs Enhancer that just rolled out today. It's causing the Dark Theme to be applied to the nav bar even if you don't have it enabled.
I've submitted a fix to the Chrome Store this morning. Hopefully it will be approved in the next day or so.
Sorry for this! I had things working but the header changed again yesterday which introduced this bug.
Update: The new version has been approved and this will fix the issue with the Dark Theme being applied to the nav bar. This also fixes Shopping Spree Mode.
The new version is 3.8.6
Please message me here or email me: [email protected] if you find any other issues :)