Multiplayer Health Bar

I'm making an FPS game, and right now just want a placeholder UI for player health.

In order to do this I'm following this tutorial. I also added a health regen mechanic to keep things interesting.

Here is my code:

 public class PlayerHealth : NetworkBehaviour 
 {
     public const int maxHealth = 100;
 
     [SyncVar(hook = "OnChangeHealth")]
     public int currentHealth = maxHealth;
 
     public RectTransform healthBar;
 
 
     void Start()
     {
         InvokeRepeating ("RegenHealth", 0.0f, 1.0f);
     }
 
     public void TakeDamage(int amount)
     {
         
         if (!isServer) {
             return;
         }
         currentHealth -= amount;
         if (currentHealth <= 0) {
             currentHealth = 100;
             //Debug.Log("Dead!");
             GetComponent<NetworkedPlayerScript> ().RpcResolveFall ();
         }
         //healthBar.sizeDelta = new Vector2 (currentHealth, healthBar.sizeDelta.y);
             
     }
 
     void RegenHealth()
     {
         if (currentHealth < maxHealth) {
             currentHealth += 5;
         }
     }
 
     void OnChangeHealth(int health)
     {
         healthBar.sizeDelta = new Vector2 (health, healthBar.sizeDelta.y);
     }
         
 }

To be clear, the actual health syncs from player to player. It is the health bar itself that is causing some issues. For example, when a host hits a client, both the client and host's health bar goes down. When the client hits the host, neither health bar changes.

Am I missing something here? The health bar is a canvas attached to the player if that clears anything up. I'm just honestly so confused as why this doesn't work. Since the actual health syncs up, I'd imagine getting a health bar to work would be easy. Any suggestions are welcome!