Leaking shower - grout problem?

[DrFoxtrot]

Hello,

I've ripped up the landing carpet to prepare for new carpet to be fitted tomorrow and discovered this patch. On the other side of the wall is the en suite shower and I thought the grout looked ok to the naked eye but the photo with flash (and zooming in) tells a different story. Would cracks like this result in leakage like this or could something else be wrong?

What should I fix/ replace it with? I've read on the internet about only certain grouts being waterproof? Is that right ? Any advice welcome please.

This happened in our last house. I watched a couple of YouTube videos on how to replace the grout between tiles, went and bought a grout removing kit from B&Q and a tub of ready mixed grout and it was an easy fix. If you have the time, try regrouting the tiles and see if that stops the leak. If it doesn't, it probably means the sealant around the top of the shower tray has gone. That is another relatively easy fix, but it's time consuming and you can't use the shower until the replacement sealant has cured.

Thanks. How far up the tiles did you remove grout, did you just do the ones that looked like it needed it or the next row up as well?

I just did the ones where the grout had cracked. It was pretty obvious which were the issue.