Super thrive is wonderful stuff if used properly. From day 1 I like to use 1 drop/ gallon, and guarantee you it does boost growth by just a touch, a touch for a cheap product is worth it to me.
On another note Fox farms ocean forest is wonderful soil, even for seedlings. Though I have heard of a few people having minor problems with seedlings in it, so some strains may not like it. I have planted many seeds in that very soil, and had great germination rates, with wonderful healthy growth all the way through. It's really good soil, if you dont know how/ dont want to mix your own soil (My preference).
This has been my experience with these 2 products, I love em!