Refresh iTunes metadata on songs purchased from the iTunes store
For songs you purchased, check to see if iTunes in the cloud allows you to download again the songs from the store.


http://support.apple.com/kb/HT2519 - Downloading past purchases
http://support.apple.com/kb/HT5085 - iTunes in the cloud availability per country


If so, delete all the incorrect purchased tracks (making a backup of the computer just in case) and then re-download the affected tracks.