I just did a little research. It would seem the high THC/low CBD is caused by the farming technique:

"However, modern growing techniques have also affected these chemical levels. For example, illegal growers have turned to indoor marijuana farms to avoid detection. Growing cannabis locally in such farms also circumvents the need to import the drug, and guarantees a more reliable harvest. However, the 24-hour lighting used in these farms inadvertently reduces CBD levels in the plant."[0]

[0] https://www.theguardian.com/science/blog/2014/jan/17/cannabi...