Aperture: Not all photos syncing to phone

So, I recently got back from a trip and uploaded all photos to Aperture. I then connected my phone to sync. Now, when looking at Photostream, all pictures are showing up. However, when looking at the particular album, only 33 of the 38 photos appear. What could be causing this? Is it because I edited some? And if so, why would they not appear?

Thanks,
-anthony