Interesting shower room problem

[Nollys]

So we have damp on both sides of our shower cubicle in a ground floor shower room that's been added on as an after thought to our flat. We've recently moved in and noticed that the damp has gotten a lot worse with daily use of the shower. There is a window and a good extractor fan in the room.
Looking at the cubicle it's a bad installation - there is a gap on both sides at the bottom of the cubicle, which I will seal up.

They also use normal paint on the walls, which has peeled in the damp areas.

When I tap some of the tiles they sound hollow whereas others sound deeper or more solid.

I don't know whether I need to replace the hollow sounding tiles. There is no sign of cracks or gaps around the hollow sounding tiles. But the damp patches on both sides are at the same level as these tiles.

Thoughts? Do I replace the tiles or just seal the gaps and repaint and see how it goes?

 

[Nollys]

Any help guys?

 

[RogerBoyle]

Do it properly would be my advice
Strip it back, remove the damp materials.
If necessary get a dehumidifier on the go for the walls
Then redo it with appropriate materials of your choice

 

[tpt]

second that. strip it back see what the issue is, then backerboard or tank and re tile.