theres different kind of white spots, if u dont mind tell me details about ur plants, outdoor or indoor? if outdoor, can be from little birds, or pest, white bugs, spiders love hang on it thats how white came on it, clean it with fresh water from bottled water be sure they get full sun, or be sure they not hot in light system, check ur finger for heats from light ray if too hot, pull it up little bit plants gotta to be cool theres 10 or more different kind of white spotting i need know more about yours