The way those lines look uneven, I might suspect the media. Have you tried this print on another media? Try a quality media like a cast 3m or Avery product (or both). If we can rule out the media, then I would say to print some solid blocks of each primary color - Cyan, Magenta, Yellow and Black to see how well the heads do while firing constantly each color. Then I would check the calibrations starting with the mechanical ones and then the electrical ones.
Then, to answer your questions, yes, the head could be going bad, and yes this could be caused by the dampers. But I would rule out the above items before we went to parts replacement. When was the last time you replaced the cap tops? I'd start there - they should be changed at least once a year, then look at replacing the dampers and then the printhead.
Good Luck