Matty
Maybe best if I could tell you about the environment where I grow my St Swithins. First of all, they get a lot of light, maybe as much as 3000 foot candles during a bright summer day. I do not see any leaf damage at these levels. I have good air circulation with a sturdy fan only 10 feet away from the plants. The winter temps are down to 61 degrees and the summer temps are whatever it is outside. Three years ago it hit 107 degrees. I did not see any lasting damage to the multiflorals. My humidity can be as low as 25% on a hot, dry summer afternoon, but the rest of the time it is usually above 50%. I don't think I've ever seen it at more than 75%. I fertilize with water that is 80% RO and 20% tap. The tap water is about 300 ppm dissolved solids, mostly calcium and magnesium carbonate. I use Michigan State fertilizer and the TDS of the final solution is about 225 ppm. 60 ppm of this is from the tap water. I also add dolomite to any of the paphs needing limestone. I not very careful with the amount, and I suspect that most of it washes out the next time I water. Nearly all of the paphs are potted in Orchiata.
As you can see none of this approaches the optimum conditions for these plants, but it is the best I can do on a sustainable basis.
Good luck with your paphs, I'm sure you will be successful.
Mike