But if you want to give it a shot using extreme alkaline like Sager
tsunami with a lot of agitation and dwell time but low pressure maybe 6 00 or so through your two jet wand..
Then use a strong acid to brighten it up such as prochems or sagers or whoever else's just mix it couldn't strong..
Then put down as many fans as you got and watch the efflorescence occur which is a given it'll happen in random spots in the grout as well as some areas on the tile itself let it dry for a few days then come back and try and brush it all off or pad clean it but if you get it wet again it's going to start all over
Just tell them this is all going to happen so there's no surprises or finger pointing it's just a fact of life when you're cleaning terracotta clay tiles that are super absorbent and get over mopped virtually every night..