Hey chew seems like one of those ferts you want to break up and mix into your soil beforehand. you want to get it nice and spread out through the soil, but at this seedling stage it might shock the plant to transplant it into new soil. These things are kinda use at your own risk you know i think what the plant needs / likes has a lot to do with genetics too somehow. it might make your soil retain more water, so you have to be quite diligent checking your watering schedule. made the top of my friends plant's bucket get covered in moss once haha. It's actually not a bad thing btw, but it was kinda off putting. 🚀 use at your own risk but i wouldn't ever leave my cal mag far away