Hey Hillio! The one thing that comes to mind right away when I read your post is pressure / tension with the fretting hand (generally left). Make sure you are only using enough pressure necessary to fret each note / chord when you are playing or practicing. Not only does this help to prevent injury and increase efficiency, but it may lighten up on your calusses.

I believe that there is generally always at least a light calus on each of the four fingers. This is natural.


Chris