I agree with GK. But sky, a plant grown for 40 days in veg, has already been mature and the switch in lights after 2 weeks will or should show sex yes. however a plant that is set to flower after 1-2 weeks is not mature and has to gain a muturity level before it can start to flower, it needs to build up its harmones and chemicals before it can produce bud, 40 days is alittle long to me for vegging i keep it 25-30 days, but due to the immaturity of the plant it may take a month just for the plant to sex. giving it an extra week or 2 in vegg seems more benificial, let it mature and when u swith to flower it is fully ready to go. honestly any one can do this, if you really think you can get good results show us and i will shut up