I am unsure how the nitrate fertilizer kills a Paphiopedilum. I was told by Xavier Garreu de Loubresse to avoid NO3 fertilizers for Paphs., as it will cause many defficiencies, with the ultimate result being death of the plant. Being that it's XPGDL, there will be supporting research and analysis upon nitrate fertilizer use on Paphiopedilums. XPGDL is reknown for his superb and complete Paphiopedilum collection, and his studies, research, and analysis upon cultivation of the genus.

-Pat