Music/ iTunes issue with downloads

I have been syncing my Mac and iphone regularly. Especially syncing new songs. When I was researching another issue I discovered a few songs that I purchased needed downloading

i already had them on my Mac and iPhone, and now I have 2 copies of theses songs. I did need to (re) authorize the Mac to download them, but it was already authorized? Will music/apple/MAC eventually clear them?

*the related issue was that I’m 80% sure I bought an album in 2004 (it’s release date) and it’s not part of my library, and it’s not showing up in purchases. I haven’t changed my account ( just the password several times over that much time). Any idea on other ways/places to check.