Melee Area Attack - Object reference not set to an instance of an object

Hello everyone. I'm trying to set up a combat system, but I've got stuck with a weird error.

 using UnityEngine;
 using System.Collections;

 
 public class PlayerAttack : MonoBehaviour {
 
     public float attackTimer;
     public float cooldown;
 
     // Use this for initialization
     void Start () {
         attackTimer = 0;
         cooldown = 2.0f;
     }
     
     // Update is called once per frame
     void Update () {
         if (attackTimer > 0)
             attackTimer -= Time.deltaTime;
 
         if (attackTimer < 0)
             attackTimer = 0;
 
         if (Input.GetKeyUp(KeyCode.F)){
             if (attackTimer == 0)
             {
                 FrontAttack();
                 attackTimer = cooldown;
                 }        
             }
 
         if (Input.GetKeyUp(KeyCode.G))
         {
             if (attackTimer == 0)
             {
                 AreaAttack();
                 attackTimer = cooldown;
             }
         }
     }
 
     private void FrontAttack()
     {
         Collider[] colliders = Physics.OverlapSphere(transform.position, 2.5f);
         foreach (Collider target in colliders)
         {
 
             Vector3 dir = (target.transform.position - transform.position).normalized;
 
             float direction = Vector3.Dot(dir, transform.forward);
 
             if (direction > 0)
                 {
                     EnemyHealth eh = (EnemyHealth)target.GetComponent("EnemyHealth");
                     eh.AddjustCurrentHealth(-10);
                 }
             }
         }
 }

The function FrontAttack works properly. So I thought "let's copy an paste the function, name it AreaAttack, change the radius of effect and remove the direction part so it can damage at 360°".

 private void AreaAttack()
     {
         Collider[] colliders = Physics.OverlapSphere(transform.position, 8f);
         foreach (Collider target in colliders)
         {
 
                 EnemyHealth eh = (EnemyHealth)target.GetComponent("EnemyHealth");
                 eh.AddjustCurrentHealth(-5);
         }
     }

But if I try it I get "Object reference not set to an instance of an object" referred to the line which define eh in the AreaAttack function. And if I press "G" repeatedly it damages the enemy, without waiting for the cooldown :(

Here I also paste the EnemyHealth script:

using UnityEngine; using System.Collections;

 public class EnemyHealth : MonoBehaviour
 {
     public int maxHealth = 100;
     public int curHealth = 100;
 
     // display healthbar
     public int left = 10;
     public int top = 40;
 
     public float healthBarLenght;
 
     // Use this for initialization
     void Start()
     {
         healthBarLenght = Screen.width / 2;
     }
 
     // Update is called once per frame
     void Update()
     {
         AddjustCurrentHealth(0);
     }
 
     void OnGUI()
     {
         GUI.Box(new Rect(left, top, healthBarLenght, 20), curHealth + "/" + maxHealth);
     }
 
     public void AddjustCurrentHealth(int adj)
     {
         curHealth += adj;
 
         if (curHealth < 0)
             curHealth = 0;
 
         if (curHealth > maxHealth)
             curHealth = maxHealth;
 
         if (maxHealth < 1)
             maxHealth = 1;
 
         healthBarLenght = (Screen.width / 2) * (curHealth / (float)maxHealth);
     }
 }

I seriously can't understand why this happens. I would like to know if someone can tell me the reason and maybe offer me another solution (I would like to avoid using something like a list of targets btw). Thank you a lot for the attention. If you need other parts of my tiny project ask and I'll be pleased to post them :)