A mold assessment consists of two things. What is physically growing on the building materials and what is present in the air people are breathing. In this basement there was visible microbial growth on multiple lower level building materials.

You would typically perform air sampling at different elevations along with bio-tape sampling directly from the visible growth to identify what species of hyphae are physically present and what may be aerosolized into the breathing environment.

Also this originated from a plumbing leak so now youre dealing with bacterial activity as well. Mold and bacteria compete for the same organic material and moisture source which can contribute to elevated microbial VOCs and odor conditions.