Some iCloud screensaver photos appear soft

I'm using photos from an iCloud Photo Album for my screensaver slideshow. Most of the images look great but a few look very soft.

If I go to the actual image in the stream Settings/General/Screensave/My Photos/Type My Photos/My Photos and click on the Album I want to use for the stream, I can scroll through all the photos in the Album and the photos in question look fine.

Any idea how I can correct this so they look good in the slideshow?