Don’t turn the exhaust on. You’re too early in the grow to worry about co2. When that becomes a factor you have already ceased worrying about humidity being too low. If temps are too high without the exhaust, dim the light and move closer. All presumes your lights themselves don’t need exhausted. If that’s the case, you either live with the low humidity* or dome the sprouts and spritz the inside of the dome as frequently as needed.
Hellraiser reports no issues with low humidity and seedlings, and he lives in a desert.
While your seedlings are really small I would put a humidity dome over them.
I use these little propagation trays. I put the pot on top of a lid so it’s not sitting in the water below so it doesn’t get too wet. The lower water and the heat pad make it a rain forest in there.
You could take a clear 2 liter bottle and cut it in half to make a dome. Use the bottom half.
