Question
I put them in a shed where it got to about 0 degrees in the winter. Also there were 4 of them. The species were purpurea, danas delight, leucophylla,and pscittisina.

Answer
Hi Tommy,

Since you only have four Sarracenia, I recommend finding a cool window, preferably North facing, for those plants to spend the winter.  If you have them right up in the window where it's cold, they will get enough of a dormancy to meet their needs.  During dormancy keep them damp, but not as wet, and watch for mold.  Frequent top-watering will help prevent mold too.  Clip off any dead leaves.  

Using a windowsill will allow you to see the plants and monitor them.  Both being in your shed, and the refrigerator have similar risks which are fungal infections because of being in the dark, and just forgetting about them.  The ones that passed away over the winter in your shed could have been from cold, mold, or some of both.

As your collection grows you may need to consider setting up your plants to spend the winter outside.  Because you're in a fairly cold climate zone, it will require tarps and mulching for the winter, or building a bog garden.  We have detailed information in our volume #1 DVD on what that looks like.  Here's another resource that is very helpful:  http://www.carnivorousplants.org/howto/GrowingEnvirons/BogOntarioCanada.php

Good Growing!

Jeff Dallas
Sarracenia Northwest
http://www.growcarnivorousplants.com