Peace lily leaf tips die for several reasons. Frequently the problem has a combination of causes. 1. Salt damage: Salts from irrigation water or from fertilizer accumulate in the soil. Excess salts are carried to the leaves and deposited in the tips of pointed leaves like those of peace lily plants. When enough salts accumulate there, the leaf tip dies. 2. Plant too dry: The leaf tip, being farthest from the roots, is the first part of the leaf to die when the plant does not get enough water. 3. Toxic salts: Some chemicals, especially soluble salts, are damaging in very small amounts. They accumulate in leaf tips as other salts do, killing the tissue there. The most common of these toxic chemicals are chloride, borate, and fluoride.