I feel like I would have gotten a faster and better root growth in the beginning if I had planted the seeds into Jiffys instead of small rockwool cubes. I think the rockwool was just a bit too moist for optimal root growth and also having the rockwool cubes in a propagation box kept the moisture inside the rockwool longer than I would have wanted, so the roots didn't really need to start searching for water.
So the beginning was a bit slower than I would have liked but that's on me and next time I remember to use Jiffys for seeds and rockwool for clones.