Hi weed

You are using Canna TERRA Professional Plus. Canna Bio products are more suited to the Canna BIO Professional Plus medium, although they have been developed for soil use. It may be an idea to switch to the Terra products, as they have been developed specifically for the medium you are using. They also have a new product - Canna Flush - which can be used in all types of subtrates.
Are you using tap water? If so, do you let the chlorine evaporate before feeding?