I am inclined to think that you aren't taking divots because of the overtaking rate of the clubhead. By that, I mean that you are letting the clubhead pass your hands at or after impact. Also, you could have your weight and CoGs positioned too far behind the golf ball in the downswing and well as at impact. You should always, ALWAYS, contact the ground with irons, especially short irons, unless you are trying a specialty shot.
Without actually seeing you swing a club, however, this is merely speculation. Just thought I would throw in my 2 cents about why it might be occurring.