Pink textures in the Tile Palette

I created and added six textures to the GrassPlatform Tilesets. I named them in sequential order beginning with GrassPlatform_TileSet_26.
https://i.imgur.com/KSIU40J.png

After dragging the updated Tileset into the existing Grass Platform in the Tile Palette, seven random pink tiles appeared.
https://i.imgur.com/JqqV7sZ.png

That afterward updated everything in the Scene. I'm at a loss here.
https://i.imgur.com/xJlFgte.png

Short of redoing each tile again,...

Pink textures in the Tile Palette