I'm not sure what to do about the white particles, but I think that the leaf problem you are describing sounds like over watering. The easiest way to kill this plant is by watering too much. Hold off on the watering for a while. This plant likes to get bone dry before it gets watered again. Watering frequency depends on where you are keeping the plant (humidity levels, light levels, etc). I water mine every week and a half to two weeks, but I've heard of people watering as little as once a month. Also, check your pot drainage. I put my plant in a clay pot and that seems to help.

Well I have another suggestion, I would take the plant out of the potting soil, and see what those roots look like, it may have had rot when you purchased the plant. If the roots look good, put it back into dry mix and don't water for two weeks, if you are lucky you can save the plant. Check that potting mix, if it has peat moss, no wonder it is dying. I water as little for the whole winter here or they rot, they will not tolerate damp soil, with cold conditions. They need very fast draining soil, and temps. no lower than 55F. Or no water at all from October 1 to April 1 if you live in a cold climate. Some take very low light, other lots of sun. Clay pots do dry out faster, that was excellent advise. Use a chop stick for a water meter or a pencil, put in down into the soil at least 3/4 of the way, lift it out and feel if the bottom is damp. Don't water from the top, it doesn't like water in its face. (vase) I made my share of mistakes over the years, but I learned from them. Good luck with your plant. Norma