Question
I think that i have over fed my peace lilly now its brown what can i do to save it

Answer
One of the MANY hazards of Chemical Fertilizers it the way they burn roots and leaves of innocent plants.  DRENCH the pot with water to wash out the fertilizer and minimize the rootburn, to the extent that is possible.  Most people will tell you to be more careful.

A product called Messenger, invented at Cornell University, might help your plant repair itself.  I have not used it yet -- it is something I did not quite believe until I read the research that led to its development.  It's not an enzyme, it's not a fertilizer.  It's a protein that educates a plant on repair and immunization.  I think if there is anything left of your Peace Lily, once you have finished making the soil nontoxic by drenching, dose your plant with this stuff.  It's hard to find, but not impossible, and you can probably find it online.  Let me know how it goes.