2D Platformer, Jump on the enemies to kill them.

I'm creating a 2D platformer in Unity. I'm trying to get the player to be able to jump on the enemies head in order to destroy them. In order to test if the player is jumping on them or not, I'm checking whether the player's y position is higher than the enemies' y position via this script. The issue I've ran into is that with multiple enemies in the scene, it seems to only track the lowest enemy, so the player is able to kill any enemy that is high up by simply colliding with them. Is there a better way to handle this?

 void OnTriggerEnter(Collider c) {
         
     GameObject player = GameObject.FindWithTag ("Player");
     GameObject enemy = GameObject.FindWithTag ("Enemy");
 
     if (c.tag == "Player") {
         if (player.transform.position.y <= enemy.transform.position.y + 2) {
                 c.GetComponent<Entity> ().TakeDamage (10);
                 }
         if (player.transform.position.y >= enemy.transform.position.y) {
                 Destroy(this.gameObject);
                     }
                 }