Bad seedling start.

They’re fine, just continue to water as usual. As long as you don’t keep switching up the light cycle and you don’t use less than the 18hrs of light the seedlings are too young to really be impacted.

They will take 24 hrs at this stage without problems anyway.. no harm done. Not in 1 hour increments as said bellow..UV... haha I also thought that at 1 point too.. that's how we learn...

looks fine

All plants, autos/photos, vegging or not, NEED a dark period..........however, your plants will be just fine now that you have gone back to 18/6. They will need to be pottted up quite soon, their current pots are small and will be stunting growth in a weeks time. The myth that it is ok to grow cannabis at 24/0 is just that......a myth!

Very stressful for a plant to have her timings messed up, I used to think that lowering the hours from 18 to 12 in daily increments of 1 hour would benefit as it would mimic nature better, turns out it causes hermies, 😀 . She will be fine jist don't make a habit of it. It can have unexpected results. P.S anytime a leaf curls up with a crispy tip its overheating, heating faster than it cools, make sure you got oxygen is those little pots. Best of luck.

Vegging plants don't need a dark period so no harm done.