Although I have grown this plant in the past, It has been a while so I did a quick goole search and have the following link for you.

http://www.thegardenhelper.com/peacelily.htm

If I had to take a quick guess I would say that maybe you are not letting the soul dry out just slightly between waterings.

If the soil is not draining well and the roots stay too wet this particular plant will lose leaves.

I hope this helps.

John

I often tell people to "listen to Mother Nature, her advice is best". In the wild, this species (and your plant is almost certainly a hybrid since hybridizers have created more hybrids than there are species) is found on the fringes of rain forest. They don't get as much rain as plants within the forest. They like to dry between watering but they do feed fairly heavily. I don't try to grow them in my atrium because it is too wet. But I do grow two in my office. If there is a neglected plant in the house (and I've got hundreds and hundreds) these are the ones.

I water about once every week but sometimes once every 10 days. When I water, I give it a really good drink. But then I wait for the soil to dry well on the top before any more water is offered. I keep the plants near a window but they only receive diffused late afternoon light. Little else.

I offer them fertilizer about once a month, but only a very dilute feeding. Other than that, they are truly neglected. The only reason I keep them is they were a gift from a family funeral.

So what is my advice? Don't fret over the plants. Pot them in pots just slightly larger than their root system but use a potting mix that will drain very fast. Make sure the pots drain quickly. Don't let the roots ever sit in water. One potting mix I've found that works well is a mixture of Miracle Grow Moisture Control Mix in a mixture of 50% Miracle Grow, 20% peat, 10% orchid potting media that contains both charcoal and gravel, and 20% PerliteÂ. Mix this mixture well and water as described. Other than that, leave them alone. Chances are, the plants will recover.