O
One Day
To answer your original question though, how to rectify it. It all needs taking up. Replace the ply with something stronger that's not 6mm ply. if you've damp issues, I'd suggest overboard the floor with 10mm wedi board. Or ditra membrane.
And most important, get a tiler in who knows how to prepare properly!
And most important, get a tiler in who knows how to prepare properly!