drdawg said: Aidan.
If you don't mind, would you re-state your problem but this time, really go into detail? I grow a lot of rubber trees and have for decades. I should be able to help you with your problem, or at least explain what's going on, but I need a lot more information. From the time you changed your plant's routine to now, tell me everything that you did, that Mother Nature did, and that you saw along the way. Tell me exactly what you observe now, even if it is only a trunk and branches. There should be a time-frame here as well as conditions during that time-frame. I don't guess you have any pictures of those leaves before they exfoliated? Good, close-up pictures of the remaining trunk and particularly the branch tips might be helpful.