Edit in JSFiddle

var game = new Phaser.Game(600,500,Phaser.CANVAS,'gameContainer');

    var GameState = function(game) {
        this.stoneGroup = null;
    };

    GameState.prototype = {
        
          preload: function(){
            this.load.spritesheet('stone','http://s8.postimg.org/uemiyw52d/stone.png',72,72);    
            this.load.image('bg','http://s8.postimg.org/prggx4hph/background.jpg');    
          },
        
        create: function(){
            this.physics.startSystem(Phaser.Physics.ARCADE);
            this.add.sprite(0,0,'bg');    
            this.handlestone();  
        },
        
        handlestone: function(){
            this.stoneGroup = this.add.physicsGroup(Phaser.Physics.ARCADE);
            for(var i=0;i<=5;i++){
                var stn = this.stoneGroup.create(this.rnd.integerInRange(20,550),this.rnd.integerInRange(0,-50),'stone');
                    stn.body.velocity.x = this.rnd.integerInRange(-50,-120);
                    stn.body.velocity.y = this.rnd.integerInRange(50,150);
            }
            
             this.stoneGroup.setAll('anchor.setTo',0.5);
             this.stoneGroup.setAll('body.setSize',55,55,0,0);
           // this.stoneGroup.setAll('body.velocity.y',this.rnd.integerInRange(-50,100));
            
            this.stoneGroup.callAll('animations.add','animations','rotate',[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18], this.rnd.integerInRange(12,50), true);
            this.stoneGroup.callAll('animations.play','animations','rotate');
            //this.stoneGroup.setAll('outOfBoundsKill',true);
            //this.stoneGroup.setAll('checkWorldBounds',true);
        },
        
        wrapStone: function(stone){
             if(stone.y>500){
                 stone.x = this.rnd.integerInRange(-20,550);
                 stone.y = this.rnd.integerInRange(0,-50);
             }
        },
        
        update: function(){
          this.physics.arcade.overlap(this.stoneGroup);     
          this.stoneGroup.forEach(this.wrapStone,this);
          
        },
        
        render: function(){
            this.game.debug.text('Living '+this.stoneGroup.countLiving(),32,23);
            this.game.debug.text('Dead '+this.stoneGroup.countDead(),160,23); 
        }
    };

    game.state.add('MainGame',GameState);
    game.state.start('MainGame');