-Try toeing the pads a little. It looks like the pads are either parallel to the rim, or the rear of the pad is touching slightly; make the front of the pad touch first.
-Clean the rims thoroughly (simple green and/or rubbing alcohol) and sand the pads down a little (to get rid of contamination).
If none of the adjustments suggested in this thread help:
-Those are cheap pads. Consider upgrading to cartridge style pads with aluminum holders.
-I also prefer Vs to Cantis. You would need to swap your brakes to 'Drop V' levers in addition to the brake calipers.