Bend your knees a little more, in your perturn, shift your weight to the front of the ski to slow it down a little, and then decisively comit to your secondary (bouy) turn and let the ski do its work! You look like you are forcing the ski around the turns which will then stall the ski at the end of the turn, which causes lots of tip, leaving you off center which will make you want to sit on the back of your ski, creating a vicious cycle.
Summary, 1.) don't force your turns 2.) stay centered with eyes and shoulders level.
Hope this helps!