How long till I can tell sex?

I have 4 seedlings 2 weeks old, 2 throwing tons of new leaf and growth, other 2 are the runts of the litter. I switched them all to 12/12 lighting today under my 400 watt HPS (I actually have the thing running overnight to keep them warm during the cold nights). My question is, when should I expect sex organs to develop? My guess was withing the first couple of weeks but I might be wrong.

when you start flowering, at 3-4 node take clones, then flower those, for 8days-2weeks, and ull know for sure

at just 2 weeks old, it could take a month or longer for you to see the first sign of flowering.

i f you have the patience let them age till they pre flower 6-9 weeks take some clones from each plant around 5th 6th week... by the time they show sex you'll a lot more than one female to flower