You could see if using distilled water or collected rainwater makes a difference. You could try more water; or less water. Less sun. Was it a young plant when you never had the problem? And is it older leaves that are going brown? It's going to have to lose leaves. Just because it's evergreen doesn't mean that all those leaves stay there forever. Old ones die and new ones come along.
With the help from this form, I followed up by boiling my water before I set it aside. That seemed to work. I now have shoots popping out.
I've had problems not with peace lilies but with carnivorous plants which are more sensitive. For those I fill a plastic milk jug with water and allow it to stand for 24 hours with the cap off to allow the chlorine and/or fluorine to dissipate. That seems to do the trick. You may want to try that instead of boiling the water.
