Hi, I'm new here and also new to growing tropical bonsai. This past summer I purchased a ficus and a chinese elm. I have both plants next to windows on my second floor. Both plants are losing their leaves at an alarming rate. I'm not sure if this is normal or not? I have the heat vent in that room closed so it doesn't blow directly on the plants(the temp in the room is about 67 degrees all the time) and I have made sure not to over or under water them so I'm a little concerned. Any ideas?