Are the blooms opening up this way? Or are they getting this way after being open for awhile? I was told once, but it wasn't proven, over fertilizing the plant when it is setting blooms can result in this. I say it wasn't proven simply b/c I feed mine everytime I water, w/ a very weak solution, when I cut back on the feeding, it stopped blooming, I started feeding again and it started to bloom. It hasn't had green centers since. My PL is 6 years old and it is one of the biggest I have ever seen.(4' wide x 4' tall)

I would cut the blooms off and try to get it to bud again and see what happens. There is probably another opinion on here, this is just my personal experiance.

Mine did this once also. I'm not sure why but I thought it was kind of cool. Mine is a varigated peace lily.
I would be worried about the black spots...are you overwatering?

It's probably age. When the flowers first emerge, the spathe and spadix are both white. As time passes, both parts of the flower change from white to cream to green to black/brown (not necessarily in unison). It'd be meaningful if they were already black when unfurling, but it doesn't mean anything if they started out white and have just changed. They don't generally stay white for more than a week or two.

I haven't had it long enough to really open up many blooms. But from what I can tell, they're opening white and fading to black (had to get a Metallica reference in there). I haven't fertilized the plant at all so I don't think that would be the problem.

So the big lily at the top...when that goes brown and dies, I trim it back. Does another one come back to replace it?

Mine usually just fade to light brown and shrivel up after about a week. Yes cut it off as far down as you can. Another may come somewhere else.