it does look like pm. remove leaves immediately surrounding the infected area and burn or put in a plastic baggy and get rid of them. if it gets worse try to get some Serenade organic fungicide. GL
cool plant! i always surprised how much stretch i get out of C99 plants. put them in flower at 12" and the just grow like hell right up to harvest. you'll get some fine smoke from the Mekong.
the plant as shown in the pot looks really nice. i would bump up the nitrogen amounts. the fan leaf pic shows calcium deficiency and it's hard to tell but maybe some mite damage.
i agree with harris hawk about nutrient burn. the plant were too young for nutes especially when using worm castings.
the castings are good to use as a supplement but they do contain a good bit of nitrogen. i always mix a bit of castings to my potting soil but i use it on close to the bottom...