Delete instantiated prefab

The thing is I have multiple instantiated prefabs at the same time and instChest = Instantiate(chest, chestSpawnLeft.transform.position, Quaternion.identity); won’t work for me

Would you mind to post your code ?

maybe if you are instantiating many prefabs with a loop or something, you are overwriting instChest reference to the instantiated object.

You could have each prefab delete itself through scripts on the instantiated object. I have done this before:

public class Ore : MonoBehaviour
{
    ...

    public void OnDepletion()
    {
        Destroy(gameObject);
    }
}