are they like salt grains? if so it could be ick. an increase in temp to 85 degrees C, and aquarium salt can cure it. But let us know what it is first b4 doing anything so we can be sure!
thats how I treated and they were fine in a few days!
sounds like ick. i have cured it before. All the above is true, just make sure you treat long enough because the ick is a parasite. when you see the symptoms (white spots) the parasite is at the end of its cycle and the salt only works on when the parasite reproduces which happens every couple of days. It is important to treat for a few extra days once symptoms subsided to kill all the parasites.