Action Script 3. Multiple stages are like 1

Action Script 3. Multiple stages are like 1

I'm creating simple flash game, where character move on the ground and
here are some stages where can jump.
But here is problem, all stages are like 1 object that's why character
flying on the air. (see at image)

All stages are called: ground3 Here is part of code where character
jumping and stay on the ground:
if(Hero.y_speed>0 && Hero.hitTestObject(ground3)){
Hero.y_speed=0;
if(space){
trace("You clicked SPACE");
Hero.y -= 80;
}
Have you any ideas how to fix It?