Scrolling background overlapped - unity3d

Question

I have long background for game so I have made two partition of it and started implementation of scrolling one after another.
But during scrolling, I was facing this kind of issue - one part get overlapped on other part, following image will give you more clearance about my point:
Because of overlapping problem, its not looking smooth.
Here is the code that I have used for implementation:
public class LayerScroller : MonoBehaviour
{
public Layer[] backgroundLayers;
public Layer[] starLayers;
void Start ()
{
}
void Update ()
{
// for (int i = 0; i < backgroundLayers.Length; i++) {
// backgroundLayers [i].MoveLayer ();
// }
for (int i = 0; i < starLayers.Length; i++) {
starLayers [i].MoveLayer ();
}
}
}
public class Layer : MonoBehaviour
{
public Transform prevGroupLayer;
public float speed;
public void MoveLayer ()
{
Vector3 currPosition = transform.position;
currPosition.y -= speed;
transform.position = Vector3.Lerp (transform.position, currPosition, Time.deltaTime * 10f);
// transform.Translate (Vector3.right * -speed * Time.deltaTime);
if (transform.position.y <= -GameConstants.BACKGROUND_LENGTH) {
Vector3 currentPosition = transform.position;
currentPosition.y = (prevGroupLayer.position.y + (GameConstants.BACKGROUND_LENGTH)) - speed * Time.deltaTime;
transform.position = currentPosition;
}
}
}
LayerScroller script is controlling all child layers and each layer contains Layer script.
Complete hierarchy looking like this:
Please give some guidance for solving this overlapping problem, definitely I am doing some small mistake.