Bicarbonates for mildew and fungus

[YAgo]

Hi guys, I need to ask Ray if Potassium Bicarbonate could work as a fungicide with phalaenopsis in LECA.
My Orchids are generating an infection from the Crown into the base of the leaves, making them squishy, transparent and weakening completely to the point that the whole plant separates from the crown.
I have been cleaning the LECA with water and Clorox, rinse well, and the plants have been submerge in Physan20 (2 tsp per Gallon). After drying I submerge them agains in water (with SuperThrive, 2.5 ml (per gallon) of SuperNova Grow an Subcultures M and B) twice a week and then placed on top of a heat mat. The Orchids have been on top of the heat mat for almost 3-4 weeks for 24/7.

I don't know what else to do, I'm loosing already 5 phalaenopsis already. New rots start growing, but they fall pray of this infection.

Please I need some help.
Thanks

Yago