Some of them have to be mixed in the specific order step by step, or it ruins the whole feeding. I remember one of my general hydro nutrients always went in the bucket first. Also, a "three part" generally has 3 to six more parts for a balanced diet too. It could have had a glaring omission, like no cal-mag etc.
Only problem I have had with Jack's classic; I thought my sprayer was over a half gallon, it is really more like 1/4 gallon. I double fed for weeks and got minor but irreversible clawed; and dark green leaves. Still yielded ok, and smoked great.