"Comments are always welcome!"
I know everyone wants to keep it 'organic'. But the listener today has been 'trained' to expect in tune vocals.
I'd suggest running your vocal tracks through a pitch corrector that will 'gently' nudge things in tune. I use Melodyne.
Hopefully the two voices are on separate tracks, to do that.
You don't need to over-correct, but get the two voices to settle in tune prety quickly. The problem is mostly evident because the notes are held long (half-notes, quarter-notes).
Send me the two vocal tracks and I'll do it for you - FREE! Then you can judge.