Unwanted dark edge around RenderTexture

Using the code below i'm taking a screenshot of a designated area using a rendertexture, and saving it as a PNG. Unfortunately no matter what i do i keep getting dark edges that are 1 pixel wide. Somtimes it's on the bottom, and sometimes it's on the bottom and left. Depends on what resolution i save the image.

My camera settings are Depth only and Orthographic. The size varies depending on the device aspect ratio, but it doesn't seem to matter

Anyone ever get this problem when using rendertextures?

here's the problem illustrated-

         void OnPostRender(){
      
             if(takePic){
      
                 Texture2D tex = new Texture2D (width, height, TextureFormat.RGB24, false);
                 RenderTexture rtTemp = RenderTexture.GetTemporary (width, height, 0, 0,RenderTextureReadWrite.Default);
      
                 cam.targetTexture = rtTemp;
                 RenderTexture.active = rtTemp;
      
                 tex.ReadPixels (new Rect(0, 0, width, height), 0, 0);
      
                 tex.Apply ();
      
                 byte[] bytes = tex.EncodeToPNG();
                 Destroy (tex);
      
                 string pngfilepath = MenuManager.screenShotDataPath + MenuManager.currentScreen + @".png";
      
                 File.WriteAllBytes(pngfilepath, bytes);
      
                 RenderTexture.ReleaseTemporary (rtTemp);
                 takePic = false;
                 gameObject.SetActive(false);
             }
         }