I made  a batch of frosting that doesn't seem to be setting up in the fridge as well as I would like. should i add more confectioners?

thanks.

Why are you setting it up in the fridge?  Is it still in the bowl or already on a cake?  If it is still in the bowl and too soft to work with, refrigerating it will only delay the problem as it will soften when it warms up to be served.  If it is too soft when you are done mixing it, then add more  powdered sugar, not refrigerate it.