it looks like overwatering ,with underwatering the leaves start to dry out begining at the tips and i dont see that when did this occur morning or night , time, and how long after watering did it occur harvesthetic im on my way setting up a scrog so keep the thread updated as im following wth great intrest and any info you got would be of great help and very pro mate keep it up,and as freind owl said i woul repot with a better draining soil mix best off luck mate i will pray to nebula the god of all mary jane plants and ask her to spread a little love your way ,lol best of luck mate and keep it up