I agree with Tara. The droopy one looks to me like the "root-ball" has been allowed to dry out, and when this happens, it soaks up moisture very slowly. I don't think that it's a sun issue though. I would soak this plant in a sink or a bucket of water for an hr. to get that root-ball re-hydrated. It's practically impossible to tell when these plants have dried, at least visually. Get used to picking up the plant when it is dry and then again when it is well-watered. You can tell by the weight when it needs water.
