Fluoride Can Damage Plants
Brown leaf tips on these and other sensitive indoor plants may be due to fluoride in the water, over fertilization or improper watering.
Reduce damage by using distilled, rain or other water free of fluoride. Water collected from your dehumidifier is another option as long as you are not cleaning it with toxic chemicals that could damage the plant.
Avoid using potting mixes with perlite if fluoride is a problem. This puffy white addition to potting mixes provides needed drainage but also contains fluoride. Use a potting mix with a different gritty drainage material.
Fertilize only as needed. Slow growing plants in low light conditions need less fertilizer than the actively growing plants in bright light.
A bit more information: Reduce the buildup of salts by leaching the soil. Water thoroughly and allow the excess water to drain out of the pot. Wait 20 minutes and water thoroughly again. Repeat one more time.