Textures not applying properly.

I'll try to make this as concise and short as possible; please bare with me.

I made a square plane, its UV, and then different diffuse maps for it. Then, I made a ''dungeon'' copying that same plane. All of that on Blender. I then moved the finished dungeon into unity, so I could start putting the done textures into it. I select all the floor planes, put its floor diffuse map, but everything gets affected by it (walls and ceiling planes).

I have over 1k planes, so putting textures (diffuse, normal, etc) one by one is not a choice. What can I do to apply just the selected textures into the tiles of my choice? Anything than doing it one by one is acceptable.

Thanks a lot!