imagemin for gruntjs used with watch for grunt not properly watching my files

What I would like is the watcher to watch any newly added images and compress ONLY the newly added ones. I would also want it to remove the images I remove from the uncompressed folder (which is images/images/), also in the compressed one which is (images/build/), but this doesn't happen.

What happens now is, anytime I add an image, Grunt recompresses them all (as in this screenshot:

where I added two new images, and it recompresses the whole folder) and if I remove an image from the uncompressed folder, grunt keeps them in the compressed one.

Here's chunks of my gruntfile:

• the task

  imagemin : {
      dynamic : {
          files : [{
              expand : true,
              cwd : 'images/images/',
              src : ['**/*.{png,jpg,gif}'],
              dest : 'images/build/'
          }]
      }
  }, //end imagemin
  

• the watcher part:

  images : {
      files : ['images/images/*.{png,jpg,gif}'],
      tasks : ['imagemin'],
      options : {
          spawn : false,
      }
  }
  

do I need an additional plugin to do this? thanks in advance!

you can use
- grunt-newer for detecting updated files : https://github.com/tschaub/grunt-newer
- grunt-delete-sync for synchronize deleted files between two directories https://www.npmjs.org/package/grunt-delete-sync