Songs are greyed out with a dotted circle next to them and won't sync
I added some songs to my iTunes library today from CDs and downloads outside of iTunes. There are also other songs that aren't working which have been purchased from iTunes via my phone. I've been trying to sync them Ito my iPhone 5 for hours but they won't. My iTunes is set to sync the whole library and they are ticked as well. They appear fine in the library and play but when I go to my phone and 'on this iPhone' they are greyed out and there is a dotted circle on the left of them. All the other songs are going onto my phone fine, it's just these ones. My iPhone is on ios7 and I updated iTunes to the most recent version today before trying to sync. How can I get them to sync
iPhone 5, iOS 7