I just replaced my Black Panther 7 bearings with new Bones Swiss bearings, the difference has me wanting to go back to the blk panthers. The wheels are just not spinning. I actually slow down when I bomb "the hill". I read the inset w/ the package about how these bearings need a break-in period, yet I have skated for two days on them with little improvement in wheel speed and have lost my stoke. Could they be a defective set?