Leaf Ache Type 2 w/ Gigantic Picture

I fail...at life >_<. I see bits of this on all four plants, what could be the meaning? Again, maybe dust or something? I sometimes see crap from my walls or fan dust crap on my plants here n there. Hmmmm...I'm sorry for being so bothersome woo big pictures! (look at the middle)

Look at this site and figure which picture your plant resembles:

Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos