Thanks!
I suspected the brightness was filter-related. Such effects are far more obvious when looking at the various shots of the same scene side-by-side.
Sorry about the "old pictures." This is also more obvious on the Rover website, and I'm not diligent enough to track all the "time" numbers on the photos. It's frustrating when they go a week or more between updates on the Rover website.
Were the shots in my first post also older?