Do tiles need resurfacing/refinishing?

[CadburySpira]

We had our bathroom redone about 7 years ago now with very nice Porcelanosa tiles, they were matte and perfect for us as we have very hard water and they didn't show up the splashes. Now though, they are starting to show water marks a lot more noticeably. Has the matte surface worn out? Do tiles need resurfacing normally? I've tried looking on the Porcelanosa site but I can't see anything, I'll try and email them but I just wondered if anyone else had this?

Ok, I've discovered they are ceramic tiles and I should not have used bleach on them. I've only started using Flash bleach on them recently because the grout was starting to discolour, how annoying. I still can't seem to find out what kind of product I should be using to reseal them or if I need to get a professional in.