Indeed, the brown spotting on the leaf looks like a calcium deficiency.
Try a flushing and then use some cal-mag supplement to help, cannabis loves calcium and magnesium too, so I generally use a supplement all the time to help.
anyone still following this thread? if so help me out.... I have same prob but is it possible that my well water has locked out the cal? i have very hard water
distilled, R/O, or just collect rainwater. Bad water will kill your grow. Get your PH straight before you attempt anything else, or you are doomed to fail