1st Grow - stunted growth?

Maybe the starter pot is too big, and they are shooting roots instead of growing. I think I can remember something like that in a book I had. Hope this helps or gives a hint. Happy growing

Let the dirt dry. But if u have a fungus in the dirt u might be fucked. Any time I've had fungus my plants die. You should try using grow bags they let the roots breath and it's way easier to dry them if u over water.

Jeg vil også sige for meget vand Og sikkert en ph værdi der står stille på 7.0.. Og hvis din lampe ik er kraftig nok så hænh dog laver bror. :-). 😉. Happy grow og held og lykke

To already be dealing with a gnat issue in your first couple weeks, it's safe to assume you were watering way too much and probably stunted root growth. If the issue is corrected(let it dry our some), then there's probably still a little time for these to rebound but they'll probably still finish on the smaller side.

To deal with gnats in a growing environment its best to use BTi or Nematodes. they will kill them all in a week or two. repeat applications maybe needed in a few weeks but its cheep and effective, Sand can work if its an even later across the medium but all the added extra weight of it compresses the substrate. Your plants do look a bit small. maybe they need more food, best to start a diary and link it to the questions you ask so others can have a better understanding of whats happening. Good Luck!