Generally speaking, I think folks that are having issues overdo it with disinfectants, bactericides, and fungicides. In the vast majority of cases, the true issue is poor culture, often due to ignorance of the needs of the plant or I attention to the fact that something has changed. One major example is when dealing with root rot.
Healthy roots don’t get attacked by microbes, weak ones do. The minute the inexperienced grower sees it however, the fist thing they want to do is “treat with something” such as Physan, hydrogen peroxide, or a fungicide, thinking that by killing the pathogen, the roots will recover, which they won’t.
The sequence is poor culture > weak and dying roots > adventitious microbes come in to “clean up the mess”.
I’m not saying that there aren’t cases in which a pathogen is somehow introduced to the collection and does damage, but relatively speaking, those are rare, and in those cases, it is more often bacteria than fungi.