Thanks for stopping by! It sounds to me like you should try using some essential oils! I've used them in the past with mild success but I didn't spend as much time as I should have keeping an eye on the plants.

Essential oils for plant fungus

Linked above is a quick article I found but many of them say the same things: rosemary oil, tea trea oil and castile soap are great at helping reduce or eliminate plant fungus. I would love to find out if this worked for you, so if you try it let me know!