2 Player Snake Game Not Working

Hey, I created a simple snake game a while ago, it works, but when I import two players(different controls and prefabs) they can only die by touching their own line and not the enemies. why is that, the code shows no errors. using UnityEngine; using System.Collections; using System.Collections.Generic; using System.Linq;

public class Snake : MonoBehaviour {

 Vector2 dir = Vector2.right;
 public Sprite rightdoge;
 public Sprite leftdoge;
 bool ate = false;
 List<Transform> tail = new List<Transform>();

 public GameObject tailPrefab;

 void Start () {

     InvokeRepeating("Move", .06f, .06f);    
 }


 void Update() {

     if (Input.GetKey (KeyCode.RightArrow)) {
         dir = Vector2.right;
         GetComponent<SpriteRenderer> ().sprite = rightdoge;
     } else if (Input.GetKey (KeyCode.DownArrow))
         dir = -Vector2.up;
     else if (Input.GetKey (KeyCode.LeftArrow)) {
         dir = -Vector2.right; 
         GetComponent<SpriteRenderer> ().sprite = leftdoge;
     }
     else if (Input.GetKey(KeyCode.UpArrow))
         dir = Vector2.up;
 }

 void OnTriggerEnter2D(Collider2D coll) {

     if (coll.name.StartsWith ("foodPrefab")) {

         ate = true;

     
         Destroy (coll.gameObject);
     } else {
     
     }
     if (coll.name.StartsWith ("border")) {
         Destroy (this.gameObject);
     }

 
     if (coll.name.StartsWith ("tail")) {
         Destroy (this.gameObject);
 
     }
     if (coll.name.StartsWith ("secondtail")) {
         Destroy (this.gameObject);

     }
     }


 void Move() {

     Vector2 v = transform.position;

 
     transform.Translate(dir);


     if (ate) {

         GameObject g =(GameObject)Instantiate(tailPrefab,
             v,
             Quaternion.identity);

     
         tail.Insert(0, g.transform);


         ate = false;
     }

     else if (tail.Count > 0) {
 
         tail.Last().position = v;


         tail.Insert(0, tail.Last());
         tail.RemoveAt(tail.Count-1);
     }
 }
 }