I just came out from BIC.
with my broken Japanese I managed to get the staff to exchange one for me.
he brought my set to compare with the sample set, and agreed that my set was slightly more blotchy and had bluish spots at the top. so I got a new set, and though it still had slight discoloration, it's was visibly better than the first set. so I kept the new set.
do all set show some form of discoloration?