I duuno too much though a response is always a good thing.

What I read about LST is that should be started before the plant gets to ridged. and way before the 12/12

What I have heard 12/12 can be started when you are half way with the height of the plant you want. (the taller the more real estate for buds) This is also the time you find the sex of the plant. look around - you'll find what you need in most sections. Growing take ALOT of research - mostly all right on tnhis site with good grow logs and documentation. Like all plants it uses the NPK - the plant needs mostly N and P right now. every other week with nutes.

you probably need some N from the yellowing of leaves - plants do need food so if you haven't been I'd get some to it - just not too much to kill it !

after 12/12 give it some P & K not so much N.