Hey there friend,
I see that the leaves are also curling upwards on the sides, yes?
Usually this is due to, under watering/overwatering, extremely low/extremely high humidity, or other issues with roots.
45% humidity is a little low but not bad for this stage in veg, typically you want around 55%avg or slightly higher during veg.
From what you’re saying, she most likely just needs more water especially to penetrate deeper into the root zone.
This link may help as well!
https://www.growweedeasy.com/serrated-edges-curling-up