Change value of a static variable multiple times in one script

I'm spawning a number of different sized enemies that move at different speeds. I control the speed with a variable called speed in another script.

I'm trying to instantiate multiple different version of said enemy with different speeds. As seen below:

level1GM.cs

 using UnityEngine;
 using System.Collections;
 
 public class level1GM : MonoBehaviour {
 
     public GameObject enemy;
     Vector3 size9, size17;
 
     void Start () {
         size9 = new Vector3 (0.0f, 0.0f, 8.0f);
         size17 = new Vector3 (0.0f, 0.0f, 16.0f);
 
         enemyMovement.speed = 6f;
         enemy.transform.localScale += size9;
         Instantiate (enemy, new Vector3(-20.0f, 0.0f, 5.5f), Quaternion.identity);
         enemy.transform.localScale -= size9;
 
         enemy.transform.localScale += size9;
         Instantiate (enemy, new Vector3(20.0f, 0.0f, -5.5f), Quaternion.Euler(0.0f, 180.0f, 0.0f));
         enemy.transform.localScale -= size9;
 
         enemyMovement.speed = 4f;
         Instantiate(enemy, new Vector3(9.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(2.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(-1.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(-3.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(-5.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(-7.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(-9.5f, 0.0f, 25.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
 
         enemyMovement.speed = 4.2f;
         Instantiate(enemy, new Vector3(-9.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(-2.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(1.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(3.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(5.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(7.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         Instantiate(enemy, new Vector3(9.5f, 0.0f, 32.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
 
         enemyMovement.speed = 7f;
         enemy.transform.localScale += size17;
         Instantiate (enemy, new Vector3(-1.5f, 0.0f, 37.0f), Quaternion.Euler(0.0f, 90.0f, 0.0f));
         enemy.transform.localScale -= size17;
     }
 }

enemyMovement.cs

 using UnityEngine;
 using System.Collections;
 
 public class enemyMovement : MonoBehaviour {
 
     public static float speed = 1f;
 
     // Use this for initialization
     void Start () {
         Destroy (gameObject, 15f);
     }
     
     // Update is called once per frame
     void Update () {
         transform.Translate (speed * Time.deltaTime, 0.0f, 0.0f);
     }
 
     void OnCollisionEnter (Collision col){
         if (col.collider.tag == "Player") {
             Debug.Log ("Death");
         }
     }
 }
 

But it will only use the last enemyMovement.speed because of course it's in start. But how would I go about having different speeds of different instantiated objects? Would I need a variety of different prefabs?

Thank you.