I have a mango tree I have grown indoor from seed since march of 2008. Recently I have noticed a blackening/brownish of the tips of some of the leaves. The leaves are even starting to curl. Underneath some of the leaves, on the main vein, there is black spots. I assumed this was a fungus problem so i sprayed the whole plant with a fungicide but im not sure if it's working. I water my tree only when the top soil layer is dry which happens every week or 2. I really dont want to lose this plant! I have included a few photo links below if that helps. Any help or advice will be greatly appreciated!

http://tinypic.com/view.php?pic=301zv69&s=4 (leaf tip)

http://tinypic.com/view.php?pic=21khzx3&s=4 (leaf tip)

http://tinypic.com/view.php?pic=2dhyb7q&s=4 (black spots)

http://tinypic.com/view.php?pic=v4m7vd&s=4 (the tree)