I hate collar rot! Help! How do you prevent it?

[Maru777]

Hello everyone! I need a bit of advice because I am currently having a meltdown because of this blasted collar rot. 6th time it happens to me (over 4 years, bit still). There must be something that I am messing up here because there is a pattern. Every time a plant got this is was a new plant that I repotted after purchasing. Various media - bark for some, lecca and SH for some others. I never got this on a plant that I had for a while and also it only seems to happen after I repot them because for ex 2 of the 6 I repotted about 2-3 weeks after buying and that was when they got hit. It’s so weird. Out of the 6, 3 I saved (though set back significantly because I had to cut pseudobulbs out before the thing spread), 2 I lost and one I am currently struggling with. It’s always the sympodials - though blessedly not all of them that I bought and repotted that had issues. I do live in a highly humid and very warm place but that seems fine for the ones that make it past the first repot. I’ve repotted the others dozens of times and they are fine and so are the new ones that do not get it on that first repot. Sigh! What do more experienced growers do? Anything that does not involve very heavy chemical use I would be wiling to do - I have a couple of tiny frogs that came from God knows where and live in some of my pots so I am careful with the chemicals I use to not kill them. They are cute Is there any hope that I can avoid this happening again? When I see that unholy buttery color I want to cry