I have a large Peace Lily plant that is slowly dying. The leaves are turning brown, one by one. They are not drooping, so I don't think it needs watering. I have it about 6 yards from a north-west facing window, so I don't feel like it is burning from the rays. What else should I do/check?

As plants age, there is some "dying off" of especially lower leaves…Are these older/lower leaves that are browning? If so…I'd say that it is a normal process…And nothing to really be concerned with…Cut them off…If, on the other hand, these are leaves in the middle or upper part of the plant…Then a picture may be of help.

Agree with Tara. However, sometimes symptoms of over and underwatering affects the leaves similarly. So if it were my plant, I will check the soil & roots, just to be sure it is just moderately moist. Or sometimes the soil may be gradually clumping up, so it is slowly suffocating the roots, so slightly tease the soil, add some perlite, so there is some airflow there.

Peace Lily is very resilient. I had one that looks pathetically dead after being left outdoors in summer, but it gradually recovered with careful nurturing in the shade and kept moist.

Welcome to All Things Plants!

Do the leaves turn from green to brown, or do they go from green to yellow to brown?

Does the whole leaf turn color simultaneously? Or is it starting from the edges and progressing inward?

The more clues you can give us, the better our answers will be.

Perhaps it needs re-potting?

Repotting may help, but without knowing the cause of the problem, one cannot say for sure.

I don't know where you live, but lower temperatures or drafts or heavy blooming can trigger dormancy in these plants, and it resembles a plant that's dying. Browning tips, drooping or dying leaves can last for a month of two. Plants will begin growing again if you keep them moist but not wet and place them in bright filtered light out of possible drafts. I hope that's the case and you're not losing the plant.

Is the plant in an air conditioned room?

to ATP.

Water may indeed be the problem. Not enough water actually. In nature, Spathyphyllums grow in sun and water. Not knowing your growing zone and conditions does make it difficult to say exactly what the problem may be. Have a look at this info from Exotic Rainforest. Perhaps you will find it beneficial to you.

http://www.exoticrainforest.co...

Peace lilies seem to be sensitive to chemicals in water. Are you using chlorinated city water? I was pleasantly surprised when I moved from the city to the country and switched to well water, because many of my tropicals improved immensely. I've worked in offices where people brought their plants in because the water at their home wasn't as good as the water in a different water district.
I use straight well water on my plants, not the water that goes through the water softener. Each well is different, of course, but chemicals or minerals in the water could be the source of your problem.