Nested for loop isnt working

Hi!

I have a "System.Serializable" in which I store information about the diffrent background layers. Now I want to add to them a parallax effect. But it dosn't work as it should be and I don't really understand why.

I have shrinked it down to the bare essentials:

 public BackgroundData[] datas;

     void Update () {
         for (int i = 0; i < datas.Length; i++) {
             BackgroundData data = datas [i];
             ...
             if (distanceToCamera < data.spawnDistance) {
                 ...
                 data.backgrounds.Add (newBack.transform);
             }
 
             float addPos = player.rigid.velocity.x * data.speedFactor;
             for (int j = 0; j < data.backgrounds.Count; j++) {
                 data.backgrounds[i].Translate (Vector3.left * addPos * Time.deltaTime);
 
                 Debug.Log (data.backgrounds[i].gameObject.name); //<-- always the same
                 Debug.Log (data.backgrounds.Count); //<-- increase right
             }
         }
     }
 }
 
 [System.Serializable]
 public class BackgroundData {
     [Range(0,1)] public float speedFactor;
     ...
     [HideInInspector]public List<Transform> backgrounds = new List<Transform> ();
 }