My guess:
Either those two tracks have a different artist, e.g. 'featuring' another artist - fix would be to select all the tracks in iTunes and set the album artist the same for all.
Or, iTunes is being an arse and not syncing everything properly - I've been getting a weird red square in a circle against some tracks on my iPhone lately with a corresponding greyed out track with dotted circle in iTunes. Resolution for me was to uncheck "sync music" in iTunes and then resync everything again.
Or it could of course be something completely different.

More importantly, what's the album?
