It seems that no matter how hard I try, I can't get a lens or filter totally clean. Either the cloth leaves behind some dust or lint, or I get streaks. I use isopropyl alcohol with distilled water and a lens cloth. Can someone tell me what in the world is going wrong. I know it's the lens because if I switch from my 300mm (the one I found the problem with) to my 70-200 or my 18-55 the specks in my pictures disappear.