I have grown from a small transplant an Impatiens tree on my covered balcony. It is pretty tall but loses it's leaves as I think it needs more sun. The leaves are sparce, blackening on the tips, yellow, wilt and fall off. I can move to front door with partial sun if suggested. What can I do to revive and save this plant? It gave me a few pretty white flowers which were very short-lived so I am hoping to save it. Appreciate your help.