was going to say it looks like the bath tiles and silicon given way and corner section with mould. You would have been better to have a pipe leak then you would be covered under landlord insurance.
Persoanlly, as much as i love those tiles
id be buying tile paint and painting them. The edge on the bath is flat and each time you get in and out as its on floorbaords, .it will move. grout will not protect water gettin in or silicon and it will happen again.
depends on type ppl u are renting to, family maybe, but if not.....me id get rid of the bath and and install a glass cubicle with a poly base .inexpensive way
i know u didnt ask for opinion , but you dont want it to leak again. hope all goes well