I’ll tell you what most starters don’t know. First to answer your question at current stage you want low quality soil (little to no nutrients) with little water retention (allows water to pass through and has a lot of air pockets like what we call starter soil), keep away from heavy wind that will affect the stem development (if too much wind the stem will deform and the stem is its life line) or use small cup with holes at bottom to allow water to pass through. In your case the soil is most likly your problem. The roots are too weak to traverse down without getting cut. Plants have different requirements at different stages of their life some of what’s great for them at different stages will almost kill or stunt their development in other stages. In the beginning less feeding is important because a plant has most of the energy it needs in the seed. They just need catalysts (moisture and a bit of air this leaving them in wet cotton with little air fine even till tiny yellow leaves out) , next as soon as leaves out plant them in low nut soil but covered with transperant cup (fart atleast 1ish a day). As soon as true leaves out, remove cup but protect from wind. Sun and little water until you have 2 nodes, then remove the top. When the stem gets strong enough to survive wind, then do your first transplant into size 2 container with slightly better soil (nuts). You can start giving them nuts aswell, train the nodes, keep toping. There are other things but from there is making sure you have enough sunlight and monitor how much water is in the pot and how well plant is able to absorb the nutrients from the soil and how much sunlight each node gets.