Find the water
Moisture readings, thermal imaging, fan and ducting check, subfloor inspection. No treatment quoted until we know the source.
Fix it
Shower sealed, fan re-ducted through the roof, subfloor vents opened, or whatever the actual cause turns out to be.
Remediate
Contained where needed, affected porous material removed, surfaces treated and HEPA vacuumed, then dried back to a measured reading.
Report
Before and after photos, readings and the cause in writing. What a landlord, insurer or body corporate will ask for.