Check the fan first
A fan that cannot clear the steam, or that discharges into the attic, keeps putting the moisture back. An inspection should note the exhaust path, not just the growth.
Black lines in grout, a stained ceiling above the shower or a dark cabinet floor under the sink all have a simple cause: water sitting somewhere it cannot dry. An independent provider should find which one it is before quoting the cleanup.
Long hot showers in a house closed up for a Colorado winter put a lot of moisture into a small room. If the fan is weak, missing, or vented into the attic instead of outdoors, that moisture lands on the ceiling, the grout and the wall behind the tile surround and stays there.

Surface growth and a leak behind the wall look similar from the doorway, so the visit starts by working out which one you have.
A fan that cannot clear the steam, or that discharges into the attic, keeps putting the moisture back. An inspection should note the exhaust path, not just the growth.
Supply valves, drain connections, dishwasher lines and refrigerator lines drip slowly for months. Cabinet floors, toe kicks and the wall behind them are checked with a meter, not by eye.
Growth on tile, glass or a tub surround is a cleaning job. Growth on paper-faced drywall, in the cabinet base or in a subfloor means the material is affected, and that part is removed.
Grout and caulk are worth knowing about: caulk with growth in it is replaced rather than bleached, because the growth is in the material. Tile and glass clean up completely.
If the fan turns out to vent into the attic, read attic mold remediation, because the moisture is landing up there too. For a slow leak under a sink, see mold after water damage. When the musty smell follows the blower rather than the shower, the source is usually in the system itself, which is covered under HVAC and duct mold cleaning.
Larger or repeating growth is handled as described on the mold removal page, and the signs of hidden mold guide covers what to look for elsewhere in the house. Find the number to call on the contact page.
Because the room is not drying between showers. A working fan that runs long enough after the water goes off solves most of these. An independent provider should check the fan, the exhaust path and whether anything behind the wall is wet.
For light surface growth on the caulk line, yes, and new caulk on a clean dry surface holds up well. If the drywall or the wall behind the tile is wet, new caulk hides a growing problem.
Treat it as a leak until proven otherwise. A slow drip at a valve or drain can go unnoticed for months. The cabinet base is checked with a meter, and the repair to the fitting comes before the cleanup.
Call and describe what you are seeing and where the water came from to reach an independent provider.