Help brown leaves

When giving nutrients, you should do so onto moist substrate and not dry substrate. Ideally you should water first, wait an hour or two, then give nutrients. This allows the plant, especially if it has been in over dry conditions, to rehydrate itself before having to deal with fertilizers. Giving dry plants fertilizers when they are already under moisture stress (over dry substrate) will cause burning, as you have found out. I don't know the reasons for withholding water for 2 days, cannabis does need good moisture levels when flowering, however giving fertilizers to dry plants has caused the burning. Always apply fertilizers to pre-moistened substrate to prevent this from happening again. Hope this helps,...... Organoman.