Yeah mine go to sleep a bit before lights out too
5 hours? That's a bit too far away I think.
One thing I could suggest is getting them off the floor. Put something under them so their soil/root temp isn't in sync with the ground, which is the lowest and coldest part of any room. Just trying to think

because you haven't done anything to them or changed anything right? So it might be something really simple like that.
In winter my veg tent was around 19-20 degrees consistently and it was just too low to have my plants on the floor, it was making the soil and roots cold and they would droop and take ages to drink. I flipped larger saucers upside down and put my seedlings on on top so they weren't connecting with the ground and they handled the colder temps much better.
I don't know man

Its worth a shot. Young seedlings like warmer temperatures, so the lower temps of the floor might be upsetting them.