Did anyone ask you to change something? I mean - apologetically, the logic you're using seems faulty. Its the same logic as those that say 'I dont QT at all and its bullet-proof'. Im not changing anything...
I am not criticizing you or what you did (and certainly not suggesting you change something) - but you need to at least consider the possibility that had you 'done nothing' you may have had the same results. (Many people do have the same results doing nothing). That said - if I were doing QT in 2019 - I would be doing a bit of independent research on some of the new strains and issues people are having (perhaps causing QT to fail) - or at least seemingly - having a more open mind to those that are trying to help. JMHO
I’m speaking from experience that I can back up with video. Do you have any quarantine videos that I can learn from? I just find it funny that you question a lot of people’s practices like @HotRocks and @4FordFamily who have quarantined hundreds of fish and sit in the disease forum and help people all day.
For the record...
With Ich...the Trophont feeds on the fish for about 3 - 7 days...
With Velvet...the Trophont feeds on the fish for about 12hrs - 4 days....