Multi touch (help have issues)

i'm having some problems with this next stage that i'm on. I have been using MouseButtonDown but i can only pop one ball at a time. i have been looking up on multi touch and what they say just goes over my head multi touch 4 loop and hit test? i am having trouble understanding the code to go with it. what i need to happen, instead of one touch i need two at the same time. i want to know if i can keep the OnMOuseDown or if i need to change it up, also ready using a raycast? not a big fan of rays if you guys could help me i would really appreciate it!

CODE: THIS CODE IS PLACE ON THE BALLS THEMSELVES

 #pragma strict
 var tapCount : int;
 var Health : int;
 var bubbleEasy : boolean = false;
 var bubbleMed : boolean = false;
 var bubbleHard : boolean = false;
 
 
 
 
 function start()
 {
 if (bubbleEasy == true){
 
     Health = 1;
 }
 else if (bubbleMed == true){
 
     Health = 2;
 }        
 else if (bubbleHard == true){
 
     Health = 3;
 }
 }
 
 function Update(){
 
 if (Health == 0){
    
    PopBubble();   
 }
 }
 
 
 
 function OnMouseDown()
 {
     Health -= 1;
     
     //Destroy (gameObject);
 }
 
 
 function OnDestroy (){
 
 tapCount += 1;
 
 }
 
 function PopBubble(){
 
 Destroy (gameObject);
 
 
 
 
 }