Need my boolean to apply to the instance of my object instead of class

So what I want to do is: shoot a sphere that has a script on it to apply damage and explode on collision. I also want that bullet able to be charged up, but I don't want it to explode while it is being charged and is on the tip of the barrel, so I made a static boolean variable called isExpanding which returns true while the bullet is at the tip of the barrel. But my problem is that the bullets that have been fired will not call OnCollisionEnter while isExanding is equal to true, when I am expanding other bullets, so I want the variable to only apply to that instance of the bullet. Please Help. Here's my code: for the player which has movement and shooting

 //Variables individual to each player
 public static float player1DamagePercentage;
 public static float player2DamagePercentage;

 public GameObject pivot;
 public GameObject bulletEmitter;
 public GameObject bullet;
 private GameObject bulletInstance;
 private Rigidbody rb;
 private Rigidbody bulletRB;
 public static bool isExpanding = false;
 private float jumpSpeed = 50;
 private bool m_isAxisInUse = false;
 private bool inAir = false;

 private float rTriggerRaw;
 private float moveHorizontal;
 private float rsVertical;
 private float rsHorizontal;
 private float rTrigger;
 private bool aButton;
 private float xAxis;
 private float yAxis;

 void Start()
 {
     rb = GetComponent<Rigidbody>();
 }

 
 void FixedUpdate()
 {
     if (gameObject.name == "Player 2")
     {
         moveHorizontal = Input.GetAxis("Horizontal1");
         rsVertical = Input.GetAxis("Mouse Y1");
         rsHorizontal = Input.GetAxis("Mouse X1");
         rTrigger = Input.GetAxis("Right Trigger1");
         aButton = Input.GetButton("A Button1");
         xAxis = Input.GetAxis("Mouse X1");
         yAxis = Input.GetAxis("Mouse Y1");
     }
     if (gameObject.name == "Player 1")
     {
         moveHorizontal = Input.GetAxis("Horizontal");
         rsVertical = Input.GetAxis("Mouse Y");
         rsHorizontal = Input.GetAxis("Mouse X");
         rTrigger = Input.GetAxis("Right Trigger");
         aButton = Input.GetButton("A Button");
         xAxis = Input.GetAxis("Mouse X");
         yAxis = Input.GetAxis("Mouse Y");
     }

     rb.velocity = new Vector3(40 * playerSpeed * moveHorizontal * Time.deltaTime, rb.velocity.y + 0, 0);

     if (aButton && inAir == false)
     {
         rb.AddForce(0, jumpSpeed * 10f, 0);
         inAir = true;
     }

     if (yAxis != 0 || xAxis != 0)
     {
     float joystickAngle = Mathf.Atan2(xAxis, yAxis) * Mathf.Rad2Deg;
     pivot.transform.rotation = Quaternion.Slerp(pivot.transform.rotation, Quaternion.Euler(pivot.transform.rotation.x, pivot.transform.rotation.y, joystickAngle - 90F), Time.deltaTime * 5);
     }
 }

 void Update()
 {
     if(gameObject.name == "Player 2")
     {
         rTriggerRaw = Input.GetAxisRaw("Right Trigger1");

     }
     if(gameObject.name == "Player 1")
     {
         rTriggerRaw = Input.GetAxisRaw("Right Trigger");
     }

     if (rTriggerRaw != 0)
     {
         if (m_isAxisInUse == false)
         {
             bullet.transform.localScale = new Vector3(0.5f, 0.5f, 0.5f);
             bulletInstance = Instantiate(bullet, bulletEmitter.transform.position, pivot.transform.rotation);
             m_isAxisInUse = true;
         }
         isExpanding = true;
         bulletInstance.transform.localScale += new Vector3(sizeIncreaseRate * Time.deltaTime, sizeIncreaseRate * Time.deltaTime, sizeIncreaseRate * Time.deltaTime);
         if (bulletInstance.transform.localScale.x >= 1.5f || bulletInstance.transform.localScale.y >= 1.5f || bulletInstance.transform.localScale.z >= 1.5f)
         {
             bulletInstance.transform.localScale = new Vector3(1.5f, 1.5f, 1.5f);
         }
         if (m_isAxisInUse == true)
         {
             bulletInstance.transform.position = bulletEmitter.transform.position;
         }
     }
     if (rTriggerRaw == 0 || Input.GetKeyDown("w"))
     {
         isExpanding = false;
         if (bulletInstance != null)
         {
             bulletRB = bulletInstance.GetComponent<Rigidbody>();
             if (bulletRB != null)
             {
                 bulletRB.AddForce(pivot.transform.right * bulletSpeed, ForceMode.VelocityChange);
                 Destroy(bulletInstance, 2f);
                 m_isAxisInUse = false;
             }
         }
     }
 }

 void OnCollisionEnter(Collision ground)
 {
     if(ground.collider.tag == "Ground")
     {
         inAir = false;
     }
 }

Here's the code for the bullet which has all the collision detection on it

 public GameObject pivot;
 public GameObject explosionEffect;
 private Rigidbody collisionRB;

 void OnCollisionEnter(Collision collision)
 {
     if (collision.collider.tag == ("Player") && PlayerMovement1.isExpanding == false)
     {
         collisionRB = collision.collider.GetComponent<Rigidbody>();
         collisionRB.AddForce(transform.right * 100, ForceMode.Force);
         GameObject explosionInstance = Instantiate(explosionEffect, transform.position, transform.rotation);
         Destroy(gameObject);
         Destroy(explosionInstance, 1f);

     }
     if(collision.collider.tag == ("Ground") && PlayerMovement1.isExpanding == false)
     {
         Destroy(gameObject);
     }
 }

}