Snow white fungus infection

[Merita]

About 3 years ago I transplanted this plant and it was active, it bloomed normally but this year I noticed that it only had a single new growth and the roots in one part and coming out of the pot, it did not look healthy and I decided to take it out of the pot. What you see was what I found, already in other small pots I had seen it as a spider web. This fungus suffocates the roots until it ends up killing the plant. I washed the plant well, the entire back part was almost without roots and with the dry buds, I cut it and left the healthy part, put a fungicide and planted it in another pot. What else can I do?