On your website/label you advice to use PK 13/14 one week while a shop recommended me to use it more weeks?
We recommend to use PK 13/14 always for one week! CANNA feeding already contains a certain amount of P and K. When the plant is in a certain stage of the flowering stage we can't increase the feed for the plant any more, so we change the PK-ratio by adding PK 13/14 for one week.
Soak rockwool before use
Never use raw rockwool! The pH is too high. Always soak rockwool before using it for the 1st time. Soak with water or a nutrient mixture with the pH adjusted to 5 and an EC of about 1.3. CANNA Start has been specially developed for this purpose. As well as correcting pH & EC, a pre-soak also ensures an even distribution of the nutrient solution throughout the slab.