Rect from two points issue

I have a script that will draw a Rect from the center of two objects that are detected by raycast. If the center of the game object is wit$$anonymous$$n the box, then it will $$anonymous$$ghlight it red. The box draws nicely and the objects get $$anonymous$$ghlighted except for the ones in the bottom side and the right side. No matter w$$anonymous$$ch direction I make the box in (+x, +y; +x,-y etc) the bottom side and the right side are never in the box. I don't know how to fix t$$anonymous$$s. What can I do?

Rectangle script: using UnityEngine; using System.Collections;

 public class TopCamView : MonoBehaviour {
 
     public Texture2D randomtexture = null;
     public static Rect selectionBox = new Rect(0,0,0,0);
     public Vector3 originalPos = -Vector3.one;
     public Vector3 currentPos = -Vector3.one;
     // Use t$$anonymous$$s for initialization
     void Start () {
     }
     
     // Update is called once per frame
     void Update () {
         CheckCamera();
     }
     void CheckCamera() {
         //Getting firstpoint
         if (Input.GetMouseButtonDown(1)) 
         {
             RaycastHit $$anonymous$$torg = new RaycastHit();
             Ray rayorg = Camera.main.ScreenPointToRay(Input.mousePosition);
             if (Physics.Raycast(rayorg,out $$anonymous$$torg))
             {
                 if ($$anonymous$$torg.collider != null) 
                 {
                     originalPos = $$anonymous$$torg.collider.transform.position;
                     originalPos =  Camera.main.WorldToScreenPoint(originalPos);
                 }
             }
         }
         //Flipping rect if not +x,+y
         else if (Input.GetMouseButtonUp(1)) 
         {
             if (selectionBox.width < 0) {
                 selectionBox.x += selectionBox.width;
                 selectionBox.width = -selectionBox.width;
             }
             if (selectionBox.height < 0) {
                 selectionBox.y += selectionBox.height;
                 selectionBox.height = -selectionBox.height;
             }
         }
         //Getting second point (current mouse cursor)
         if (Input.GetMouseButton(1)) {
             RaycastHit $$anonymous$$tcur = new RaycastHit();
             Ray raycur = Camera.main.ScreenPointToRay(Input.mousePosition);
             if (Physics.Raycast(raycur,out $$anonymous$$tcur))
             {
                 Debug.Log($$anonymous$$tcur.collider.tag);
                 if ($$anonymous$$tcur.collider.tag == "GridUnit")
                 {
                     currentPos = $$anonymous$$tcur.collider.transform.position;
                     currentPos = Camera.main.WorldToScreenPoint(currentPos);
                 }
                 else 
                 {
                     currentPos = originalPos;
                     Debug.Log(currentPos);
                     currentPos = Camera.main.WorldToScreenPoint(currentPos);
                 }
             }
             float xdir = currentPos.x - originalPos.x;
             float ydir = InvertMouseY(currentPos.y) - InvertMouseY(originalPos.y);
             //Drawing rect
             selectionBox = new Rect(originalPos.x, InvertMouseY(originalPos.y), xdir, ydir);
         }
     }
     public static float InvertMouseY(float y) {
         return Screen.height - y;
     }
     void OnGUI()
     {
         if (originalPos != -Vector3.one)
         {
             GUI.color = new Color(1,1,1,.3f);
             GUI.DrawTexture(selectionBox,randomtexture);
         }
     }
 }

Highlight object function attached to the objects:

     void boxSelect() 
     {
         if (rend.isVisible && Input.GetMouseButtonUp(1)) 
         {
             Vector3 camPos = Camera.main.WorldToScreenPoint(transform.position);
             camPos.y = TopCamView.InvertMouseY(camPos.y);
             selectedBox = TopCamView.selectionBox.Contains(camPos);
         }
         if (selectedBox) 
         {
             rend.material.color = Color.red;
         }
         else if(!selectedBox)
         {
             rend.material.color = Color.gray;
         }
     }