Unityでにゃんこ大戦争のようなゲームを作っているのですがプレファボ化したキャラが一度Destroyするとほかのプレファボ化したそのキャラがDestroyしません

前提・実現したいこと

Unityでにゃんこ大戦争のような、わんこが主体のゲームを作っているのですが
プレファボ化したキャラが一度Destroyするとほかのプレファボ化したそのキャラがDestroyしません。

キャラクターはwankoとnyankoの2つで両方ともうまく動作しません。

わんこのtagがplayerでにゃんこのタグがenemyです。

発生している問題・エラーメッセージ

１つ目
NullReferenceException: Object reference not set to an instance of an object
Enemy+<Attack>d__12.MoveNext () (at Assets/Script/Enemy.cs:79)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <0847a0faf94444ccbaf1958021b27f54>:0)
２つ目
MissingReferenceException: The object of type 'GameObject' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.
UnityEngine.GameObject.GetComponent[T] () (at <0847a0faf94444ccbaf1958021b27f54>:0)
wanko+<Attack>d__10.MoveNext () (at Assets/Script/wanko.cs:72)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <0847a0faf94444ccbaf1958021b27f54>:0)
３つ目
NullReferenceException: Object reference not set to an instance of an object
Enemy+<Attack>d__12.MoveNext () (at Assets/Script/Enemy.cs:79)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <0847a0faf94444ccbaf1958021b27f54>:0)

該当のソースコード

C#
1Enemy.cs
2
3using System.Collections;
4using System.Collections.Generic;
5using UnityEngine;
6
7public class Enemy : MonoBehaviour
8{
9    public bool isAttack = false;
10    public bool isMove = true;
11    private Rigidbody2D rb;
12    public float EmoveSpeed = 1;
13    public float MaxHP = 2;
14    private GameObject player;
15    public float enemyHP;
16
17    // Start is called before the first frame update
18    void Start()
19    {
20        enemyHP = 2;
21        rb = GetComponent<Rigidbody2D>();
22        player = GameObject.FindWithTag("Player");
23    }
24
25    // Update is called once per frame
26    void Update()
27    {
28
29        if (isMove == true)
30        {
31            rb.velocity = new Vector2(EmoveSpeed, 0);
32            GetComponent<Animator>().SetBool("Attack", false);
33            rb.constraints = RigidbodyConstraints2D.None;
34            rb.constraints = RigidbodyConstraints2D.FreezeRotation;
35        }
36        else
37        {
38            if (isAttack == true)
39            {
40                isAttack = false;
41                StartCoroutine(Attack());
42            }
43        }
44
45        if (enemyHP == 0)
46        {
47            Destroy(this.gameObject);
48        }
49
50    }
51
52    private void OnCollisionEnter2D(Collision2D collision)
53    {
54        if (collision.gameObject.tag == "Player")
55        {
56            isMove = false;
57            rb.constraints = RigidbodyConstraints2D.FreezeAll;
58            isAttack = true;
59        }
60    }
61
62    private void OnCollisionExit2D(Collision2D collision)
63    {
64        if (collision.gameObject.tag == "Player")
65        {
66            isMove = true;
67            isAttack = false;
68        }
69    }
70
71    private IEnumerator Attack()
72    {
73        GetComponent<Animator>().SetBool("Attack", true);
74        yield return new WaitForSeconds(1.2f);
75        player.GetComponent<wanko>().playerHP--;
76        isAttack = true;
77    }
78}
79
80
81wanko.cs
82
83using System.Collections;
84using System.Collections.Generic;
85using UnityEngine;
86
87public class wanko : MonoBehaviour
88{
89    public bool isAttack = false;
90    public bool isMove = true;
91    private Rigidbody2D rb;
92    public float moveSpeed = 1;
93    private GameObject enemy;
94    public float playerHP = 2;
95
96    // Start is called before the first frame update
97    void Start()
98    {
99        rb = GetComponent<Rigidbody2D>();
100        enemy = GameObject.FindWithTag("Enemy");
101        playerHP = 2;
102    }
103
104    // Update is called once per frame
105    void Update()
106    {
107        if(isMove == true)
108        {
109            rb.velocity = new Vector2(-moveSpeed, 0);
110            GetComponent<Animator>().SetBool("Attack", false);
111            rb.constraints = RigidbodyConstraints2D.None;
112            rb.constraints = RigidbodyConstraints2D.FreezeRotation;
113        }
114        else
115        {
116            if(isAttack == true)
117            {
118                isAttack = false;
119                StartCoroutine(Attack());
120            }
121        }
122
123        if (playerHP == 0)
124        {
125            Destroy(this.gameObject);
126        }
127
128    }
129
130   private void OnCollisionEnter2D(Collision2D collision)
131    {
132        if(collision.gameObject.tag == "Enemy")
133        {
134            isMove = false;
135            rb.constraints = RigidbodyConstraints2D.FreezeAll;
136            isAttack = true;
137        }
138    }
139
140    private void OnCollisionExit2D(Collision2D collision)
141    {
142        if (collision.gameObject.tag == "Enemy")
143        {
144            isMove = true;
145            isAttack = false;
146        }
147    }
148
149    private IEnumerator Attack()
150    {
151        Debug.Log(this.playerHP);
152        GetComponent<Animator>().SetBool("Attack", true);
153        yield return new WaitForSeconds(0.8f);
154       enemy.GetComponent<Enemy>().enemyHP--;
155
156        isAttack = true;
157    }
158}