instantiate a texture2d so changes don't affect clones

What I'm doing:
Exposing a public variable for a Texture2D
Using Get/SetPixels to create a new Texture2D by 'cropping' from the source

Why (the heck) I'm doing this:
Projectors can't use sprite sheets, so I'm providing a sprite sheet to a script on the projector and using code to create a new Texture2D representing a single cell of the spritesheet.

Works just fine... until I have more than one of these in the scene, created with GameObject.Instantiate(); In that case, each new clone changes the textures used by every other clone. Quite confused by why this is happening. Advice would be awesome.

Code, stripped of nonessential info...

  public Texture2D spriteMap;  // sheet with rows/columns of individual sprites
  public int rows;             // how many rows/ colums represented on the sheet
  public int columns; 
  private Projector proj;      // projector component of this object 
  
  void Start()
  { 
 
  proj =  GetComponent(); // UnityAnswers won't let me use gt, lt signs...
 
  Material myCustomMaterial = Instantiate(proj.material) as Material;
 
  // -----------------------------------
  // info I need to randomly grab a cell of the spritesheet...
  int x = CHelp.GetRandomInt(0, columns);
  int y = CHelp.GetRandomInt(0, rows);
  int sourceSizeX = spriteMap.width;
  int sourceSizeY = spriteMap.height;
  int cellSizeX = sourceSizeX / columns;
  int cellSizeY = sourceSizeY / rows;
     
  //Trying to copy the texture rather than reference it...??
  Texture2D mySourceTexture = Instantiate(spriteMap) as Texture2D;
 
  Color[] cropping = 
  mySourceTexture.GetPixels(
  x * cellSizeX,
  y * cellSizeY,
  cellSizeX,
  cellSizeY);
  
  mySourceTexture = new Texture2D(cellSizeX, cellSizeY); 
  mySourceTexture.SetPixels(cropping); 
  mySourceTexture.wrapMode = TextureWrapMode.Clamp;
  mySourceTexture.Apply(); 
  // -----------------------------------
  proj.material = myCustomMaterial;
  proj.material.color = tint;
  proj.material.SetTexture("_ShadowTex", mySourceTexture); 
  }