Hmmm... I'm wondering if the bulb was growing under overly wet conditions when that leaf was produced? I have a papilio that was too wet and grew a leaf with the red edge like yours and some red on the top of the leaf, but not underneath... presumably a result of red blotch (for my plant, not necessarily yours). Does the red wipe off... like rust (of the plant variety, not metal)? Perhaps someone with more growing experience will have some better information! -Tina

With a lens, you should perceive some tiny critters crawling on the underside. These are Red Spider Mites. The grey dust is their skins, that they shed during their growth.