Rotate a Vector Relative to Another Vector

I'm making a runner game which scrolls forward on the z-axis. When the player clicks on a target, a projectile called bolt is fired at the enemy position. I want to have a Spread powerup (similar to Spread seen in the old Contra games), where a second bolt is fired at an angle relative to the target vector.

The problem I am having is that the second bolt ends up firing almost a mirror image (flipped on the x-axis) from where the target is when I shoot to the right, and not accurately when I shoot to the left. How can I make this work properly? Here is my existing code, in the handler for the bolt object:

 //Move bolt towards enemy
 float time = 0.5f;
 float t = 0f;
 Vector3 startPos = Runner.runnerPosition;
 Vector3 newPos = enemyScript.enemyPosition;
 newPos.z += enemyScript.speed * time;
 
 //***This line of code is not working as intended***
 Vector3 spreadPos = Quaternion.AngleAxis(-5f, Vector3.up) * newPos;
 
 switch (this.gameObject.tag)
 {
     case "FiredBolt":
         while (t < 1.0f){
             t += Time.deltaTime / time; // Sweeps from 0 to 1 in time seconds
             if (bolt != null) {
                 bolt.position = Vector3.Lerp(startPos, newPos, t);
             }
             yield return 0;
         }
         Destroy(GameObject.FindGameObjectWithTag("FiredBolt"));
     break;
     
     case "SpreadBolt":
         while (t < 1.0f) {
             t += Time.deltaTime / time; // Sweeps from 0 to 1 in time seconds
             if (bolt != null) {
                 bolt.position = Vector3.Lerp(startPos, spreadPos, t);
             }
             yield return 0;
         }
         Destroy(GameObject.FindGameObjectWithTag("SpreadBolt"));
     break;
 }