What to Do When a Radermachera (China Doll) Drops Its Leaves? Detailed Solutions

Radermachera is usually grown as an indoor potted plant, and occasionally it develops curled or yellowing leaves. What actually causes this? What should you do when a Radermachera drops its leaves? For indoor potted plants, this is caused by indoor light being too dim and poor ventilation and air circulation, unless it is the cold winter