There's a few things you should know, and theres a few things I'd like to know.
Some plants just don't branch very much. While this is true, a great deal of a plant branching has to do with the amount of light it receives. The grower can encourage branching and lateral growth by bending, training and tying down the main stem.
What do you mean you need to clone to determine the plants sex... after about 3 weeks, a plant, regardless of light cycle, will show its sex in the form of pre-flowers.
There is a WEALTH of information on this site, and you should access that information and learn it well. Much of your learning will be from experience and trial and error, since your just starting out. ( i assume)
Your plants may be growing 1 inch a day.. or stretching 1 inch a day, you have not explained anything about your setup so there I can't help much.
A picture can reveal a whole lot about a plant, so consider taking one to get further opinions.
Hope this was helpful.