redownloading previous itunes lower (128) bit rate purchases to newer bit rate (256)

I downloaded itunes purchases years ago (maybe 5 or more) from a previous macbook pro at a 128 kbps that say protected AAC Audio FIle. Is there a way to re-download these songs so they can be at the 256 kbps(with much better sound quality and that say these days Purchases AAC Audio FIle). Everytime I go to the song in the itunes store it says play onnthe place where you purchase the song as in it has already been downloaded and there doesn't seem like there is much of an option to do anything, Any advice on this would be much appreciated. Thanks!