I currently growing two gg4 s1 from seed and I will say they are very sensitive to nutrients and any kind of stress.
You have two options. Buy a basic bag of potting soil (no added nutrients), a bag like that shouldnt run you too much, maybe $10-$15. Then buy some liquid espoma organic grow and bloom ($12 each). Or if I had to pick one, the bloom. I have used the bloom in both veg and flower when I was in a pinch and waiting on my normal nutrients to come in the mail. I had awesome growth in my veg tent with that bloom.
Or just ride it out with your current soil. Use something gentle like the espoma liquid organic, you only need a capful at most per gallon and feeding once per week, that bottle will last a few months. If you buy both the grow and bloom, you add half a capful of each to a gallon of water,.