Your plant does exhibit some discoloration in the leaves but I would not be terrible concerned at this time. If by chance we are dealing with a canna virus it would not affect your other plants. I cannot positively identify the typical symptoms of the two most destructive viruses CaYMY or CaYSV. It is possible you are dealing with what some consider one of the lesser viruses or simply a nutrient deficiency. I would definitely give it a few weeks and see how the plant develops. If this is truly C. �Stuttgart, it produces leaves with segments devoid of chlorophyll. This might be a factor although I rather doubt that. If it was my plant, I would delay any decision especially since you have no other cannas. Be sure to supply adequate nutrients.

Kent

Are you sure you had no signs of virus in previous years? Regardless, the plant doesn't look like Stuttgart. Sometimes, Stuttgart will revert. If blooms aren't nice, doesn't worth saving.