Sounds like normal. My 2016 is rated at 150km and on the worst days in winter it will be around 100km so 50km range drop for winter is normal.
You don't say where you are, I'm in Ottawa, Canada so our winters can be pretty brutal in comparison with some of the other places where the Soul EV is sold. If you are somewhere that has a lot milder winter and are still getting this range loss then it may be a cause for concern.