Was it in a sunnier place before? Ficus and many others for example, will geow bigger leaves in the shade, and smaller in more light. Idk about your species, Im just passing on what Ive read and experiances with my trees. What else changed? Did you fertalize a lot or something? Changes of places, light, temp, humidity, fert, or water? I think one or more of those things could be affecting your tree. I hope that helps you. Hopefully other more experianced folks will chime in and help. Good luck, at least its growing now!

I tried as best as I could to replicate the previous setting. Sun, shade water etc.