I have the same zygo, Louisendorf. It did this when I switched to the new fertilizer (MSU-type) from my former system (Ironite, powdered milk, Epsom salts, Better-gro orchid fertilizer). Could it be nutrition or pH related? I am still experimenting with this idea. Adding the ironite and calcium back into the mix seems to be having a positive effect. If anyone figures out the perfect way to grow these....