They will droop when the leaves are "sweating" (or at least transpiring) more water out of them than the roots are taking in. This can be from overheating, having too much air movement, under watering, or having damaged the roots a little when transplanting (I notice the title is soil transplant). Weirdly it can also be from overwatering, which I believe is because the overwatering damages the roots somehow. Basically think of your plant as a straw the leaves are taking water out of the top and the roots refill that water (and adds more as it grows). Anything that interupts the roots will drop the pressure in the plant and cause wilting. With that in mind it will almost certainly just fix itself (assuming it's damaged roots) over a few days but you could (and I don't know how others on here will think about this idea) treat it a little bit like a cutting. With cuttings you take some of the leaves away to reduce the transpiration through the leaves because the plant has no roots to start with. You could reduce the number of leaves and thereby reduce the required amount of water that the roots need to keep the straw filled. It's a tough call because it's likely to just fix itself (assuming it's the roots still), but if you were planning on defoliating shortly, now might be the time.