Goldfishes are sick ! Help !?

So my goldfish been starting to grow these white little things on their fins , the white stuff that's on there fins are like little dots , that look like sand. They been acting lazy and what not laying on the bottom of the tank and then swimming for food , and they'll start chasing each other , to nip the stuff that's on their fins. I don't know what it is, please help ? and i also think its from a water change.