You might have lost points for pictures that are over 3 months old and have less than 10 views...
Pictures over 3 months old need 10 views to count towards points
...and perhaps when you checked your rank today, you updated your score and lost these points?
When was the last time you checked your point total? If it's been a while, the 3 months might have passed for a large number of images.
I could be entirely wrong, of course, but that's usually the first possibility to consider.