Using Box Store Compost or Manure For Your Worm Bin

The problem with bagged compost from a box store is - 

1. The way it is often stored...It is stacked on top of each other which compresses all the air out of the product and then they leave it out in the sun to bake.  This kills all the life in the compost, if there is any and often times will create a toxic environment because of the lack of air. 
2. Most often the bagged compost, especially like steer manure is sterilized so all of the life is killed.  They do this for fear of salmonella.  But the worms use the bedding as food stalk as well, so if there is not enough food provided the worms won't thrive.

Bottom line, always go with the happiness of the worms.  If they seem to be doing good, then I wouldn't worry, but I would try to stay away from store bought products.