I have a bc bigbud and an afghani plant and both are about a foottall in 2 gallon buckets. For the past month or so the leaves have been turning brownish and black from the edges and now spots as well all over the leaves and curling upwards. Its slowly killing my plants its worked its way up from the oldest fanleafs and now its 2 sets from the top of the plant. There is 4 fan leafs left on them that are kind of healthy but are now getting affected by this disease. I tried flushing the plant than waiting a few days and that didnt help than I tried giving it nutrients but still nothing. Nothing seems to stop the leaves from getting crispy and brown. Ive been trying for the past 3 or 4 weeks to stop this but nothing works. Ive also been to every sick plant guide that I could find on the net and still cant really find the exact deficiency or whatever it is. The deficiency that looks the most like it is magnesium but some sites definition of a magnesium deficiency looks totally different from another. Another site has a potassium deficiency that looks kind of like it. If you want to know what it sort of looks like go to google and type in magnesium deficiency and look at the bottom right picture. it looks like the tips of those leaves but its all over mine. Thanks.