I have a mangea(?) cane tree and its dying i think...?

anyway, it was doing bad, then i changed the dirt and the old dirt was moldy from too much watering. then the tree started doing better, then i watered it (maybe 6 ounces) for the first time in 3 weeks. now the leaves are turning yellow and wilting. what's going on? what fertalizers can i give it so it does better? help please!