Looking at the condition of those leaves, I am thinking powdery mildew.
Sun and dry will usually control it naturally, so another reason trees belong outside wherever possible. Neem oil every two weeks works as a preventative measure, but once you see it getting bad, it's already too late.
I have allot more experience with this in the vegetable garden than on trees, but the defoliation seems like it should at least slow it down. Definitely no repotting after defoliating, or much of anything else. I'd treat the trunk and soil with neem oil or whatever else is recommended by experienced people in your area. Otherwise the spores on the trunk will just reinfect the new leaves.