Hello, I moved into a new apartment a few months ago and last week when I removed my shower mats to replace with new ones, I noticed the shower tiles were starting to look white. I tried to scrub them, and it didnt do anything. I asked a few friends and they said it looked like hard water stains. Does anyone know if this is hard water stains? Can you tell what type of tile it is? Have any advice on cleaning it? Thanks in advance.