Leo brought this up in another current thread and I think it deserves a thread of its own. I've got a couple of sanderianum hybrids that have some yellowing leaves and one trusted grower and AOS judge thought it may be due to Phosphorous toxicity. Are sanderianums simply prone to this? Others? I'm mainly using MSU at 125N for the last year and the leaves are looking better but not great. Prior to using MSU I rotated with several different fertilizers. What are the symptoms of this toxicity and what do I need to do? My sanderianum hybrids and my Jerry Spence are the only paphs in my collection that seem bothered by it.