Need help with my tower aiming

Unity Engine
1

I am having this problem where the towers aiming are off it is pretty wierd, and I dont know how to fix it I have been told a few ways i could fix it but i dont understand how i would add it to my code, I am still pretty new to this kind of coding.
I have been told the problem with my code is in this area

if(myTarget)
	{
		if(Time.time >= nextMoveTime)
		{
			CalculateAimPosition(myTarget.position);
			turretBall.rotation = Quaternion.Slerp(turretBall.rotation, desiredRotation, Time.deltaTime*turnSpeed);
		}
		
		if(Time.time >= nextFireTime)
		{
			FireProjectile();
		}
	}
}

with the turretBall.rotation
but I just cant fix it.
and here is the whole script if you need it

using UnityEngine;
using System.Collections;
using System.Collections.Generic; 
public class Ground_Turret : MonoBehaviour {

    
public GameObject myProjectile;
public float reloadTime = 1f;
public float turnSpeed = 5f;
public float firePauseTime = .25f;

public float errorAmount = .001f;
public Transform myTarget;
public Transform[] muzzlePositions;
public Transform turretBall;

private float nextFireTime;
private float nextMoveTime;
private Quaternion desiredRotation;
private float aimError;


public List<Transform> enemiesTarget = new List<Transform>();
void  Start (){

}

void  Update (){
	

	if(myTarget)
	{
		if(Time.time >= nextMoveTime)
		{
			CalculateAimPosition(myTarget.position);
			turretBall.rotation = Quaternion.Slerp(turretBall.rotation, desiredRotation, Time.deltaTime*turnSpeed);
		}
		
		if(Time.time >= nextFireTime)
		{
			FireProjectile();
		}
	}
}


void  OnTriggerEnter ( Collider other  ){
	if(other.gameObject.tag == "Ground Enemy")
	{
		enemiesTarget.Add(other.gameObject.transform);	
		nextFireTime = Time.time+(reloadTime*.5f);
		myTarget = enemiesTarget[0];
	}
}
void  OnTriggerExit ( Collider other  ){
	if(other.gameObject.transform == myTarget)
	{
		enemiesTarget.Remove(other.gameObject.transform);
		myTarget = null;	
	}
}


void  CalculateAimPosition ( Vector3 targetPos  ){	
	Vector3 aimPoint=new Vector3(targetPos.x/*+aimError*/, targetPos.y+1700/*+aimError+1700*/
			, targetPos.z/*+aimError*/);
	desiredRotation = Quaternion.LookRotation(aimPoint);
}

//void  CalculateAimError (){
	//aimError = Random.Range(-errorAmount, errorAmount);	
//}


void  FireProjectile (){
	nextFireTime = Time.time+reloadTime;
	nextMoveTime = Time.time+firePauseTime;	
	//CalculateAimError();
	
	
	foreach(Transform theMuzzlePos in muzzlePositions)
        {
            Instantiate(myProjectile, theMuzzlePos.position, theMuzzlePos.rotation);
        }
	}
}

Just as a note here at the end, I am making a Tower Defence game

2

Your ‘calculate aim position’ is aiming at a position 1700 units above your target.