With saline implants it will typically become very clear very quickly. If there is any sort of a mechanical problem - such as an out-and-out rupture, a deflation, a leak (whether a defective valve or from any other cause) the implant will almost always continue to get smaller and eventually be completely deflated. This process can take a few weeks but more typically takes just a few days. For a couple of days you're not quite sure what's going on, and then it becomes very clear. I have had some patients who developed problems with their saline implants as a result (most likely) of mammograms but in most cases you never really fine out why it happened.
So, although it's not terribly comforting, just wait a bit. Stay in touch with your PS and it will become pretty clear pretty quickly. If the implants are not having a mechanical problem, then it's just a question of the swelling going down differently, and at a different pace (from one side to the other).
I hope that this helps, and good luck,