My bathroom floor grout has several cracks - and appears to be rusting. See the image for an exemplary area.
These cracks appear - in differing severeness - around the bathtub and along the wall, where toilet and sink are situated. The rest of the bathroom is free of these cracks.
The areas in question are not regularly flooded (at least haven't been so by me, what previous tennants did I do not know), so what comes to my mind is a busted/cracked fresh water pipe, which slowly leaks water into the floor.
Has anyone seen similar cracks/colouring before? If so, what caused them?