Your npk ratios are for a flowering plant not one that is still in veg. The nitrogen level in the canna is too low which is the reason for the N defiency. Fish emulsion is a good source of nitrogen, this can be bought at any garden store. If that is unavailable to you then get some shultz 10-10-10 (or 20-20-20) npk and give your plant a 1/2 dose of that in your next watering. You can start the canna back up when you put your plant into flower. hope this helps