I'd give them a good clean with LTP grimex (diluted 1:10 grimex:water) then reseal them with LTP MPG sealer (do you know if they have been sealed already), when this has dried use LTP waxwash as your everyday cleaner. All products are available here LTP Online | Product Basket This process will work whether your tiles have been sealed or not. Ensure to follow the instructions on the reverse of each product and follow all the advised drying times between processes.