You forgot the most important E.C. or PPM. According to picture, I can see some swollen leaves which indicates a lack of oxygen or typical overwatering(so you might need more powerful air pump). But it also looks like a nutrients problems, this is why E.C or PPM readings are important, or at least tell us how many ml per liter of canna a and b do you use? Also I know that canna aqua a and b are quite acidic, and you probably using ph up solution it's usually potassium hydroxide and it is not very pleasant stuff for plants. Instead, I suggest using potassium silicate(liquid silicone) to up your pH, it also will help stems get thicker and stronger.