JS to C# converting issues..

Hello all, I am creating a level in unity for a uni assignment; I followed this 3part tutorial a few months back: http://www.youtube.com/watch?v=1C9zbTRCWoM and got it working. The problem was when I tried converting it to a C# script so that I could use it with the PhotonNetwork.

It is working for the most part; there are no errors but for some reason the spawn times are off and all enemies after the first spawn faster than the random.range(yieldTimeMin, yieldTimeMax) which is between 1-3 seconds. I will post my JavaScript code and also my C# code(i'm not used to using for loops and yields in C# and was told something about invoke repeating would be a good idea too so if that helps then I'd love to know how I would word it into the script.

Thanks!

 #pragma strict
 
 //This Script is dealing with all of the enemy spawning such as how often, where, wave numbers etc.
 //It is placed onto the object that holds all of the spawnpoints in the game (Holder_EnemySpawnPoints).
 //@HideInInspector to hide the variable on the next line from the Inspector.
 
 
 var enemySpawnPoints : Transform[];
 var enemyPrefabs : GameObject[];
 
 var yieldTimeMin : float = 1;
 var yieldTimeMax : float = 3;
 
 var spawnXOffsetMin : float = 0;
 var spawnXOffsetMax : float = 0;
 var spawnZOffsetMin : float = 0;
 var spawnZOffsetMax : float = 0;
 
 var enemyCounter : int = 0;
 var startingSpawnNumber : int = 4;
 var isSpawning : boolean = false;
 
 var waveNumber : int;
 
 
 function SpawnEnemies(wave : int)
 {
     var spawnNum = (startingSpawnNumber + 3 * (waveNumber - 1));
     isSpawning = true;
     
     for(var i = 0; i < spawnNum; i++)
     {
         yield WaitForSeconds(Random.Range(yieldTimeMin, yieldTimeMax));
         
         var spwnObj : GameObject = enemyPrefabs[Random.Range(0, enemyPrefabs.Length)];
         var spwnPos : Transform = enemySpawnPoints[Random.Range(0, enemySpawnPoints.Length)];
         
         Instantiate(spwnObj, spwnPos.position + Vector3(Random.Range(spawnXOffsetMin, spawnXOffsetMax), 0, Random.Range(spawnZOffsetMin, spawnZOffsetMax)), spwnPos.rotation);
         enemyCounter++;
     }
     
     isSpawning = false;
 }
 
 function UpdateWave()
 {
     waveNumber++;
     SpawnEnemies(waveNumber);
 }
 
 
 
 function Start()
 {
     waveNumber = 1;
     SpawnEnemies(waveNumber);
 }
 
 function Update()
 {
     if(enemyCounter == 0 && !isSpawning)
     {
         UpdateWave();
     }
 }