assuming youve played with the grind setting (to be a little coarser than you had set for the single), i would be inclined to say that perhaps its simply a dose problem. have u checked ur dose is not too high by locking your handle in and then straight out to see if theres any impression from the shower screen? the early blondign suggests that poss. your puck is being disturbed, hence early blonding.
a vid of ur shot would be great.