physan, MSU fertilizer and demineralized water

[vyltan]

Hi all. Well am in the process of loosing my phal collection to root rot (40 of them). They are potted in thoroughly washed many times coconut husk mixed with coarse perlite 50/50, in slotted clear plastic pots. So LOTS of aeration. BUT since I wanted tremendous root system I decided to use demineralized water with proper MSU fertilizer; problem is that direct watering would take a lot of that water so I decided to soak each orchid in a pale with water/fertilizer. That still take 5 gal of water for my whole collection but it also transferred microorganisms causing root rot from one pot to another. Since I can't afford to double my water use (or triple it) by direct watering to avoid cross contamination, am thinking of adding physan to each watering. But will those quartely ammonium chemicals change pH or mineral concentration and impede fertilizer? Feel free to suggest another solution if u have one