iPhone 5S not syncing music properly, songs appear grey and "skip"

So here's the long annoying story

The other night I decided to add album artwork to a few albums that didn't have any and iTunes wouldn't recognize when I hit "get album artwork". So I added artwork manually to songs roughly A to C before realizing it was taking too long so I stopped. I plugged my iPhone in to sync.

That night I went to play some music but when I tried to play one of the tracks I edited it skipped over it. I tried playing all the others and they didn't work either. I plugged in my iPhone to sync again. No fix. I restarted my iPhone and computer. No fix. I ran disc utility (just cuz it fixes the issue sometimes) but no fix.

So I did a test (horrible decision) and decided to try syncing only "selected playlists, artists, albums, and genres" and de-selected all of the artists A - C. I synced it. And now allllll of the tracks with artists names A to C won't play on my iPhone. I've tried resetting everything multiple times with no success.

Songs that wont play appear grey on my iPhone with a red square next to them. Help?