DIY cleaning with a vinegar or diluted bleach solution is only for surface-level mold on non-porous materials. It will not address the moisture source or the mold growing within the wall cavity, which is likely here. Improper cleaning can aerosolize spores, spreading the contamination further.

A professional inspection is crucial to locate the moisture source—often a leaking AC condensation line, pipe, or poor thermal insulation causing cold spots and condensation. They use moisture meters and borescopes to see inside walls. Remediation involves isolating the area, removing affected materials like drywall, HEPA vacuuming, and antimicrobial treatment to prevent regrowth. The cost for a professional job is not trivial, as it is a process, not a simple cleaning, but it is the only way to ensure the problem is solved at its root and your air quality is restored. For health safety and protecting your belongings, a science-based approach is necessary.