if it is a soilless substrate, which coco is, and you are using "hydro" nutes that are 100% plant ready, then yes you fertilize every time somewhere around 1.3-1.5EC concentration - not counting your tap water. if nutes are not 100% plant available, then you have to treat it like soil... i don't believe that's the case here so i'm saving some typing.
this is a bottom feeding system? if so, you may need to run water throught the top occasionally. these systems are prone to buildup at the top - where the water will absorb up to, then 'ebb and flow' with evaporation depositing solids that will go back into solution the next time it gets moist = high risk of buildup over time.