Personally i'd say get your lights closer or add some more, them some stretchy plants and as for sexing, you'll be able to tell when you spot them, they usually develop in the top 3 or 4 nodes at the main trunk first (based on a plant with 10 nodes) plant maturity will depend on a lot of factors but once they start growing alternating nodes they are adult plants and should show sex even if not under flowering conditions, preflowers or pollen sacks will pop up everywhere, they both look like tiny green balls in the early stages so it's almost impossible to tell but look closely and if you see the tip split or develop a hair your in business. One thing to note is female plants are generally shorter and stockier like an indica in comparison with male plants so hopefully your stretch is from lighting! Good luck