Help needed. Issues with toilet grout

[Newbie1 0]

Hi Bros and Sis, 

I bought over a resale hdb and after renovation, the grout line on the eall starts to show some contamination. My Contractor scrap off damaged grout anf replace but the stain came back within days or in worat cases the next day. Anyone knows what is it and how to resolve? 

 

 

[MKumar 0]

U still need the svs