HELP with onEnterFrame & springing

I am trying to apply a springing formula (AS2) to 3 objects on the stage.
The function works, if i only apply it to one object on the first frame, but it “stutters” if i apply the same function to the other 2 objects as well.
Each object is supposed to come in a few frames apart.

What am i missing? - it’s driving me nuts.
Here is the code:

var spring:Number = 0.2;
var friction:Number = 0.8;
var startScale = 1;
var vx:Number = 0;
var targetScale = 100;
mc1._xscale = mc1._yscale = startScale;
mc1.onEnterFrame = mover;

function mover(){
var ax:Number = (targetScale - this._xscale)*spring;
vx += ax;
vx *= friction;
this._xscale = this._yscale += vx;
}

i want the same effect for “mc2” and “mc3”.

fla is attached

Thanks a lot in advance!!!