New bathroom advice please

[dartagnan]

Hi all, I've just had a completely new bathroom installed including plasterboarding the walls that were in a pretty bad state.
I've recently noticed I'm getting bits of black mould on the shower grouting, The grouting on the walls and flooring also goes dark when wet even though it's been painted over with water repellent.
Has the wrong grout been used?
Shouldn't it have been waterproofed grout.
My kitchen floor was tiled over 10 years ago and I've no problem with that.
Thanks

 

[Iamchamps]

How well is the room ventilated and heated?

 

[dartagnan]

Hi lamchamps, it has an extractor fan that comes on with the lights and window is nearly always left open slightly, also has a large towel radiator. It's a fairly warm room generally.

 

[JohnD]

Close the window and use the fan more.

Does it have a timer? Show us a photo please.