I just finished six layers of primer, base, and vp, all beautiful, but when I began to burnish, greyish-balck streaks appeared. these did NOT appear when I did my sample board. has anyone had this happen? The base vp was clean; I used earth pigment, a pavon trowel...I'm wondering if it was bc I didnt clean off my trowel well enough after I sanded it with my 600-grit paper. Help...