Slate tiles

Please help :?

We have slate tiles in our ensuite (dark grey) and they desperately need resealing around the open shower/ bath. DH has done a trial laquer over a small area however the grout still appears white/ light grey. Other areas where water has not hit it still have the dark grey grouting and shiny laquer.

Have we left it too late or is there still hope if cleaning it up and it looking good again?? :doh:

I am really wanting to know how can we clean up the grout as this seems to be the most stubborn??? I am hoping we don't have to dig it out and redo.

Many thanks

Sorry but you'll have to scratch it out and redo it - or stain the existing grout to match the rest but that is not a handyman job requiring a fair degree of expertise.