Just thought I would post to see if anyone else has experienced this and what they found was the cause. Could not find any visible insect pests either on the foliage or roots/bulbs, but did treat thoroughly with pest oil which made no difference. Did remove infected foliage only for it to return . Have not as yet tried a systemic fungicide or insecticide but will. Am also wondering if it could be a virus or perhaps nutritional.
Thanks for any help.