You are using 1 part of a 3 part system, you need to up the N. Their fish mix is just for this. Are you using RO or Tap? You need a ph meter and a ppm meter or you are just taking shots in the dark with your grow. Without a basis of whats going in and whats running off its hard to give you any insight other than “Yes your plants are hungry”.
There are what i feel to be a few necessities one must possess before embarking on this type of adventure. These are:
PH METER
PPM/EC METER
LIGHT METER <-OPTIONAL
GROW LOG<- To record what you see before and after feedings, and to take notation of your grow solution.
Without the bare minimun of tools above its impossible to give us the proper information we need to help you along when issues show their ugly faces.