I'm assuming you mean Peace Lily the houseplant, Spathiphyllum? Sorry if not - have you repotted in the last year or so?

Has it been fed regularly for the last 3 years? Has it filled the pot with roots? Some of the cheaper potting composts will collapse and stop drainage and aeration after a few years, too. Has the window it's in become shadier as trees grow over the years?

Thank you both for your suggestion, sad to say I should have fed it more often and perhaps repotted it as you suggested. Thanks trying to help.

According to my houseplant book, these should be split and the two sections potted separately in fresh compost every other year, preferably in Spring. You could do it now though.