Sorry for blowing up your post lmao, I'm highly caffinated at the moment and it shows.
Regarding your question about watering, when they're little like that I use a medicine dropper and water in rings around the seedling. So like, a full 12ml (its the size that comes with my kids adhd meds) around the seedling, and then extending the circle one dropper full at a time till I've watered the whole surface. Their roots grow quickly, and they will die off without moisture. Roots will not grow into dry soil. If you've got a container big enough, you can set your pot inside and bottom water as well (specifically because you didn't premoisten the soil), just let it suck it up from the bottom for a while. It can't go past the point of full saturation and it will wick up through your soil over time. Even just like 20-30 minutes should be plenty to get your pots moist enough, then take them out and let them do their thing. Running the dehumidifier more than likely has added to the pots dryness, so with that gone they should hold a good enough moisture content to see you through until your seedlings are big enough (and more importantly have enough root mass) to handle being watered fully.
Regarding your question about watering, when they're little like that I use a medicine dropper and water in rings around the seedling. So like, a full 12ml (its the size that comes with my kids adhd meds) around the seedling, and then extending the circle one dropper full at a time till I've watered the whole surface. Their roots grow quickly, and they will die off without moisture. Roots will not grow into dry soil. If you've got a container big enough, you can set your pot inside and bottom water as well (specifically because you didn't premoisten the soil), just let it suck it up from the bottom for a while. It can't go past the point of full saturation and it will wick up through your soil over time. Even just like 20-30 minutes should be plenty to get your pots moist enough, then take them out and let them do their thing. Running the dehumidifier more than likely has added to the pots dryness, so with that gone they should hold a good enough moisture content to see you through until your seedlings are big enough (and more importantly have enough root mass) to handle being watered fully.