After updating to 8.1 all my music was missing from my iPhone 6+. I thought all was well after re-syncing with iTunes but I've since noticed that I know have 15GB of 'other' space taken up on my phone that wasn't there before (The playlists I sync with my phone is also 15GB so i'm guessing that my 'lost' music is now somehow dead data just being classed as other. Any way to get rid of this?