If you're worried about using toxic chemicals, I learned this formula from this dude on channel 13. I have used it on office plants that have looked past-death and it has brought them to life. It's non-toxic yet gnats and bugs runs from this stuff.
You buy a regular spray bottle.
Pour in one small cup of LEMON dishwashing detergent.
One small cup of LEMON ammonia.
One cup of mouthwash.
Fill the rest of the bottle with water.
The lemon detergent will coat the plant and form a protective citrusy layer around it to repel bugs. The detergent also provides simple food nutrient for the plant.
The lemon ammonia will also repel bugs and the ammonia will attack any fungus on the plant and will give the plant Nitrogen when it evaporates. This gives the plant energy and helps it to process food.
The mouthwash will attack any infection that the plant may have.
First cut off any severly infected leaves and stems from the plant, then spray this solution on it. You can also pour this solution into a garden sprayer to cover a larger area, just increase the mixture dosage.
If this solution doesn't help the extent of fungus damage on your plants, it certainly will not harm them. Like I said, I used it on a plant at work that was fixing to be tossed out. It had white stuff on the leaves and stems and gnats all over it. I cut off all the moldy and infected leaves and some stems and sprayed this solutiion on it and into the potting soil and brought the plant back.