I'm not here to defend them, but I think much of this goes unnoticed in their systems due to the quick turnover.
The best thing to do IMO is medicate QTs with metro when acclimating the fish upon arrival as well as starting them out on treated food. It has increased my success rate significantly. I will be amending my QT process sticky soon to include this part of the protocol. I just wanted to be able to repeat it a few times successfully before recommending it to everyone. To which
@4FordFamily and I have done. My last batch is almost through the process now with no loss.
Another thing that I think helps is I am using pharmaceutical grade metro, not seachem.