maybe, but they look pretty sickly. Make sure that you don't have any fungus gnats or anything in the soil chomping away at root starts. Rockwool seems easiest to me. I keep them as dry as I can while keeping them moist....does that make sense? On small seedlings like that I might dribble...
Yeah, uhm not sure how you're gonna know for sure 1 1/2 months into VEG. If you want to know, sex them at 12/12. I seriously doubt that going to 20 hr. cycle caused anything to show.
One thing from the pic I see is that you have a little 6" fan pushing the hot ambient air back down. Put it under and point it up. That may not fix it all, but it will help.