Say it with me. Bleach does not kill mold. Have you ever read the bottle? Most say it is only designated for non-porous surfaces. This means that chlorine bleach can only kill surface mold.
Because mold can grow deep roots within porous surfaces, such as the grout you are observing that’s discolored, bleach will not be effective.
Chlorine cannot penetrate the growth at its roots. It just remains on the surface, while the water component of the bleach reaches further, which can actually feed the mold growth.
Grout is porous, ceramic and porcelain tile have little water absorption.
A properly constructed shower, to standards of the American National Standards Institute (ANSI), are developed by the Tile Council of North America (TCNA) to ANSI A108. Unfortunately, a vast majority of most track home builders, and multifamily developers do not follow these standards, to keep their costs low, and profits high. The result is what we are talking about, no waterproofing membrane system (ANSI A108.10), and mold.
Airborne black mold will make you sick.
Unfortunately, some people may not even be aware that they have been exposed to mold because their symptoms duplicate that of a cold, flu or a simple allergies.
If you don’t want to spend money to replace it, properly to see what you are exposing your family to by testing it yourself. Here is an Amazon DIY to see if Black Mold (Stachybotrys) exists. Have fun.
Better Choice. Hire a professional. Hire and search for a Certified Tile Installer through the Ceramic Tile Education Foundation, or member of the National Tile Contractors Association, a professional organization of contractors nationwide. You can also find consultants here to assist in litigation or insurance claims.
Builder or Developer?
See above for professional resources. Partner with a professional, and learn how new technologies in shower systems can actually save you time an money, and get warrantied systems well beyond your typical 1 year. Get it right the first time!
Renter or employee?
Have renters insurance. Call your landlord/boss, keep your receipts and medical bills, and test that mold. Find a hungry attorney, and send them to the NTCA website for a consultant and inspection further. Click on the below for some cases of mold vs. landlords.