How to Instantiate platforms with certain space inbetween each platform (Endless Runner)

Hey guys,

So i am creating a platform runner (yes like the thousands out there) and need some help. I am able to get the platforms to spawn and move towards the player. Everything is going well until i figured out the platforms will need to be different lengths.

If the platforms are the same size, they spawn with a space in between each, which is great. But if for example a very long platform spawns, it takes time for it to fully move out of the spawn point. Due to the length of this long platform, another platform will spawn on top of it which is the issue.

I need some help with figuring out how i could code and spawn different length platforms without them overlapping each other and also have a randomized space in between each platform.

Here is my current code. Now i am able to change the frequency of the platforms spawning but then that will cause huge gaps in-between smaller length platforms.

{

 public float scrollSpeed;
 public GameObject[] obstacles;
 public float frequency;
 float counter = 0.0f;
 //spawn point
 public Transform obstacleSpawnPoint;
 // Use this for initialization

 void Start () {
     scrollSpeed = 5;
     frequency = 0.5f;
 }
 
 // Update is called once per frame
 void Update () {

     //instantiate object
     if (counter <= 0.0f)
     {
         SpawnObstacle();
     }
     else
     {
         counter -= Time.deltaTime * frequency;
     }
     GameObject currentChild;


         //this scrolls obstacles
         for (int i = 0; i < transform.childCount; i++)
     {
         currentChild = transform.GetChild(i).gameObject;
         MoveObstacle(currentChild);
         if(currentChild.transform.position.x <= -15.0f)
         {
             Destroy(currentChild);
         }

     }


 }


 void MoveObstacle(GameObject obstacle)
 {
     obstacle.transform.position -= Vector3.right * (scrollSpeed * Time.deltaTime);
 }

 void SpawnObstacle()
 {
     GameObject newObstacle = Instantiate(obstacles[Random.Range(0, obstacles.Length)], obstacleSpawnPoint.position, Quaternion.identity) as GameObject;
     newObstacle.transform.parent = transform;
     counter = 1;

 }

 }

Thanks