Issue with synchronizing NPC Health over the network.

Hello there, I am facing a major problem at the moment with Networking. I am new to this tpoic, but already read a lot of theory and I think I understood it. What I do not know is the synatx and I could not find another topic in the forum so far that could help me with that.

Now my problem. I have set up soem code, that allows to set up a Masterserver and up to clients to connect. Each client controls a capsule and a third-person-camera at the moment. By pressing "1" they can apply some "Damage" to a cube that has 10 health at the Moment.

When Player 1 now damages the cube he can actually see a healthbar that shows the damage that was done. But Player 4 e.g. can not see this damage. It is somehow not synchronized. When Player 1 however "killed" the cube it disappears using "Network.Destroy". Then it disappears on all clients and the server.

This is the relevant code I use on the cube to parse his health to all clients.

 void Update (){

     if(Health <= 0){
         Network.Destroy(gameObject);
     }
 }

 [RPC]
 public void ParseBossHealth(float health){
     Debug.Log ("ParsingHealth__ " + health);
     networkView.RPC ("ParseBossHealth", RPCMode.All, health);
 }

 public void applyDamage (float damage){
     Health -= damage;
     ParseBossHealth (Health);

 }

This is the relevant code I use on each player to apply the damage:

 //Apply the done Damage to the target
 [RPC]
 public void DamageTheBoss(float damage){

     target.GetComponent<HealthScript> ().applyDamage(damage);
     GetComponent<DamageDealt> ().DamageDealtValue += damage;
     Debug.Log ("CurrentBossHealth" + currentBossHealth);
 }