yPosition kina eeauta ellipse ko matra change vaayo..?

since you are using push()function and pushing xPositionswith the value of z

try pushing the values of z to yPositionsaswell

like:

var xPositions = [0];
var yPositions = [0];



draw = function() {
var z = random(0,400);
xPositions.push(z);
yPositions.push(z);
background(69, 78, 79);



noStroke();
fill(255, 255, 255);



for (var i = 0; i < xPositions.length; i++) {
fill(255, 255, 255);
textSize(90);

ellipse(xPositions[i], yPositions[i+10], 1, 5);
yPositions[i] += 5;
}

};