I have 18" porcelain tiles in my kitchen -- a couple have cracked that I am trying to repair without removing the tiles. what began as a couple of tiles along the edge of my cabinets making a popping sound when they were stepped upon has now evolved into a couple of long cracks down the middle of these tiles. I am assuming this means the adhesive material underneath these tiles was not applied properly? Is there a to remedy this problem by drilling a couple of small holes in the tiles and squirting some kind of adhesive like material to fill in and provide some additional support for the tiles so the don't move any more?

Hello, I accidentally spilled alcohol on my slate tiles and now discoloration is apparent. Anyway I can fix this? Thanks in advance!