You're not doing anything wrong(assuming you are watering and talking to it!!) the plant is just doing what comes naturally. It is in fact indicating that the flowering cycle is coming to the end and the seeds are setting(the Spath in the centre).It will now go into its dormant period. Several things for you to do. check if the plant needs repotting - gently ease out of pot - if you see a lot of roots move into the next size. Whatever you have done, ease back on the watering, a little dry between watering. Start feeding it later on this Summer with a good fertilizer. In the natural run of things it will flower again in the Spring.