the only thing i use finish clear for is to use with glitters which its great for as its thin,i would be lost without it.however i would be lost without glaze n go it is the best thing since sliced bread and i use it for finishing all my nails.
the finish clear could be dulling because maybe you are applying not enough or to much
not having enough cleanse on the lint free pad
try curing it for longer
and make sure your brush is clean
i would probably just phone nsi anyway as they are always so helpful and im sure they can correct the problem for you.
let us know what happens though as this may help other nail techs.
good luck.xx