Sexing my plants that are in veg

I have 10 reg Qrazy Train from TGA and 5 reg Dairy Queens that are in about 2-3 veg and im wanting to throw them into flowing soon but i dont want to transfer them into the 2g pots for flowering until im really going to flowering..So can i just flip my veg lights on 12/12 then back to 18/6 to determine sex?

Thanks guys

Yes you can but understand it will take 1-2 weeks for them show 100% sure signs of male female. I have a friend that clones in bud. And then his plants take about 2 extra weeks to veg cause has to undo all the budding time. Hopefully this will be a 1 time event for you so you can just clone the fems you get from here on out. Are these clones to start with or bag seed? Cause if you have 10 and 5 and they all came from the same plant not seed you can put one of each into bud and that will tell you what the rest are. IE you wont get both male and female clones off a female plant. So if one is male they all are if one is female they all are.