How to make parameters change in an equation in a function when calling it?

I want to create a function that can generate two balls that rise at different speeds. I used the parameters of the speed in which it rises called “change” and another parameter of its x coordinates called “x”, so that they don’t originate from the same place.

If I call the function, it works, and the ball moves according to the speed I set it to. However, if I call it twice, two balls are generated but both move at the speed that I call it with the second time. In this case, two balls were generated at x coordinates 150 and 450. The first ball was supposed to move at speed y-10, and the second ball at speed y-5, but both are moving at y-5.

Therefore, they move, but the whole purpose of the code which is making it change doesn’t work. Can someone help me make it change?

void setup(){
  size(600,600);
}
float y = 600;

 void risingball(float change, float x){
  noStroke();
  fill(30,0,30);
  y = y-change;
  ellipse(x,y, 50,50);
}
  void draw(){
  background(255);
  risingball(10, 450);
  risingball(5, 250);
}