don't beat yourself up, adding EWC is far from being naïve.
The easiest course of action to net you some good herb, rather simply, would be to get a good quality bagged soil, I always had excellent luck with vermifire, it's a good soil to use, and you don't have to add much food, provided you give the plant ample soil.
Next time just get a couple bags of that, if you need to feed them the easiest, most effective, and simplest method is making teas from kelp meal, alfalfa meal, and molasses, if you use the vermifire you'd need to give them teas maybe two or three times, again, provided they have room (a minimum of 7 gallons)
Very simple, and hard to overfeed if you research it prior.
Not to mention if you grow with miracle grow, the difference between that and an organic grow are night and day.
no need to ph, no "PPMing" or any of that, those are for chem grows.
And by the way, you can absolutely burn a plant with fish emulsion, absolutely.
For that type of a nitrogen input i'd go with either fish hydrosylate or alfalfa meal tea.