Hi, it sounds like it may not be getting enough light. It's important that it have the most really bright light you can give it for up to 16 hours a day. If there isn't enough, a leaf will grow wider to catch more light, and the stems longer to reach for more. You don't need to keep the soil "wet" to the touch, that can also cause yellow leaves (and eventual rot), but when you water - from above only, not sunk in a sinkful - do it when the top layer (about 1/4 inch) is dry. It should reach all the roots (and the drain hole), if not every single time you water, then certainly most of the time, but what will keep it from staying too wet deep in the pot will be a good bonsai soil mix using a lot of grit in the mix, which lets water run through quickly so nothing stays wet for too long. A good handful of small aquarium gravel (can be 50-60% of the mix) in the soil - mixed, not layered - would be a big help. Never let the pot sit in drain water either. As far as lighting goes, what sun exposure do you have now? Do you have any supplementary lights, or just room lighting? Full spectrum fluorescents would be ideal, but without the right fixture, or enough trees to justify the expense, you might not be ready for them, so think about finding a "full spectrum" bulb (keep it only 6 inches above the tree for 15-16 hrs/day) that's supposedly a grow light, but don't just buy a "Grow light" without being sure it's a really good one.