The literature I read suggests extensive use of sulphur by orchid growers. When necessary, sulphur is used to inhibit the growth of fungus and hasten the healing process, especially on cuts, splits.
Where the fungus already exists, I would search the shelves for a fungicide with benomyl, again as recommended by the literature. Usually too, the literature recommends decreasing humidity once fungal growth is detected.
Perhaps you need to avoid leaving water in the crown of your plants. Are you watering early in the day or late in the evenings? Is the fungicide you are using systemic? I would not be familiar with the brands on your market.The only "Safer" product I recall purchasing was for the treatment of white flies on my acalypha.
Good luck with the management of the problem.