Thank you for the replies guys, several sheets over the 3sqm had changed colour once cleaned and it is a whole sheet not a mark as if it was like I had wipe a load of adhesive over and stained it, it's a perfect square! The two shades in the picture of the laid tiles are from.the same box too and like I say until cleaned they looked example try the same.
I will have a look on Monday and I've made the project manager aware, the customers have purchased over 200sqm of plank tiles from them (although they screwed up and only sent 172!) and 71sqm of wall tiles, there are these mosaics and around 5 sqm of treasures shannan mist moon mosaics all from porcelanosa so hopefully they stand a reasonable chance of an argument should the tiles be dodgy. I just can't see a sandy colour returning to grey but several things have surprised me recently lol.
Thanks again
