It would help if you could tell us the name of the soy wax. Not all soys are the same.
For storing tarts I use zip lock freezer bags. Haven't had any tarts lose their scent and they can be stored for months that way. I put them in the bags then box them and store in a dark closet. I still have a couple of bags left after 3 yrs and the tarts are still fresh smelling.