I don't have a jug so i don't know what the amounts are. I don't really know if those jugs are a complete nutrient, and i don't know what kind of ratios you are getting going by the jug instructions. Like @Dalek Supreme said about the perlite from MG, you could try watering more often. Since the ph of the solution in the reservoir could be swinging over the time of 4 days because of the instability of your nutrients or the swings caused by MG perlite. Shoot for an NPK of 3-1-2 or 3-1-3 since hempy's are a form of container growing (even though they are a passive hydro system). Without pictures most of this is just basics to try.