The short answer

Cleaning is appropriate only when the joint is intact and the discoloration is on the surface. Cracked grout, missing corners, soft caulk, gaps around fixtures, and recurring growth need a repair and moisture-control plan. A bright new bead can hide a wet substrate if the joint is not opened, dried, and prepared.

Identify the joint

Finding More likely response Why
Surface film on sound grout Clean and improve drying The joint may still shed water.
Cracked or missing grout Remove loose material and repair Water can enter behind the tile.
Flexible joint has split caulk Remove, dry, and recaulk Movement joints need flexible sealant.
Soft wall or persistent odor Stop cosmetic work Concealed moisture may be present.
Growth returns quickly Investigate ventilation and leaks Cleaning alone did not change the moisture load.

Use ventilation during bathing and allow the surface to dry. Follow product labels, never mix cleaners, protect skin and eyes, and avoid disturbing broad mold-like growth without appropriate guidance. Photograph the joint before cleaning if you may need to show a contractor the original condition.

Ask for a useful repair scope

Separate cleaning, grout removal, caulk removal, substrate drying, tile replacement, leak repair, and ventilation work. A contractor should say whether the visible joint is the water barrier or only a finish over another assembly.

Limits

This guide does not identify mold species or replace professional remediation guidance. Broad growth, sewage contamination, soft wallboard, or a leak behind the tile deserves qualified assessment.