Please small clear cups over them. If you can buy a humidity dome to cover all, then great. If not buy cups.
Make sure cups have small breather holes poked in them. This allows gas exchange and gives them fresh co2 to breathe while retaining humidity.
Also mist the cups, mist the sides only. Not the top. If you mist the top, droplets could pool and drop on your seedling thus causing light magnification on the baby's leaves and hurting stunning or even killing it.
Regarding the entire tent, you need a bigger humidifier, AC Infinity has 2 different ones the smaller one works for my 4x4 tent. Its also automatically controlled by the 69 controller.
If Temps are correct then you don't need alot of exhaust right now, stop exhausting the tent and humidity will rise on its own.
If Temps are to high then you need to exhaust, thus needing a bigger humidifier or a dome to cover all plants, or clear cups with holes for each individual plant.
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Good luck!