Once you know exactly how matabolites look it's pretty easy to tell if it's just that or if theres contamination.
That, plus subs tend to look pretty beat up after a harvest and dunk. You'll learn all these things with experience, and know the difference with a quick look and maybe a sniff.
His reasoning is sound, though. As a newer grower starting from scratch earns you experience.
Edited by Deleena24, 14 March 2019 - 02:35 PM.