Dude, i had this same shit on my plants a while back, i dont think it is burning from fertiliser, nor a deficiency. The shit i had on my plants spread from the bottom all the way to the top fucking the entire grow. I thought it was a fungy of some type. I notice from the photo that spots are appearing on the other leaves in tiny areas, and if its the same shit i had, it will infect the whole crop. I AM VERY INTERESTED FIND OUT how you go because it drove me fuckin nuts trying to get rid of the shit. I dont think its burn or defiency because the rest of the plant looks nice and green but the bottom areas are fucked which makes me think its fungul. Hope its not, anyhandle.



And as for pissing on your plants, diluted 1/10 on an outdoor plant is wonderful shit but indoors, dont even think about.