I recently received paph niveum. After few days its new leaf got rusty, I plucked out it and poured H2O2. It did not foam up. And after few days the next leaf started rusting. It is very firm.. And I used Physan and Bavastin fungicides and pesticides no luck.
Request to diagnose what it is! It is potted in moss and clay pieces. I had also made thick paste of Dithane and applied to crown, no luck.
As well as the other suggestions, we have a Delenatii which sometimes on initiation of a new fan the first leaf sometimes goes weird at the tip and we pack the center with powered cinnamon as per Harold Koopowitz in his book 'Tropical Slipper Orchids' and in no time the problem clears up. So along with the above proper potting this may be beneficial to your plant. Good luck and we hope this was helpful.
Checked with root system, the roots are almost same as at time of receiving. I received it bare root a month ago. No new roots.. but a little (2 to 3 cm of root was bit rotted)
I do not have dolomite lime or gypsum or horticulture grade limestone available in my area. Seller said he potted in CHC chips + charcoal.
Normal limestone is avialable from hardware paint store used for paints.
I have coco chips, charcoal, big bark pieces, and I crushed some sterlized egg shell to powder. I would repot in new smaller pot..