You can start flowering at anytime. Some people use a 12/12 light cycle from seed but the yields are lower. Yields are impossible to predict.

If your plants haven't reached maturity yet and you switch to a 12/12 cycle, it'll take a couple of weeks before you see pistils/preflowers with most strains. If you wait until you see alternating nodes and preflowers they will start blooming almost immediately after switching the lights.

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My first grow!!

they all got bigger pots and a new grow area with more room to work with.
and they're starting to smell like weed. yay.

they shelf theyre sitting on is removable so that gives me about 3 feet to grow vertical

are these pre-flowers?

this one is my favorite, its nice and bushy, and its leaves are short and fat, could this be indica, that would be awsome.

dude those babies are crying for the light!
got a hell of a strech
lower your lights and get those other CFLS above them.. you dont need side light for this stage..
and next time when you transplant them bury the stem into the ground to cut that strech.

ok now after lookin through your whole log Ive couple more things to say:

1.your plants are too stretched and you must stop this stretch by getting them closer to the lights(2 inch from the CFLs is perfect).
Repot them into deeper pots. When you repot bury the stem into the ground to reduce the stretch.
again move them side lights above the plants
2. Some of the curling down of the leaves is probably caused by nute burn because you are using miracle grow potting soil which is very hot for seedlings
3. In the picture you posted those aren't preflowers.. those are some sideshoot that are starting to develop.
sorry if I missed anything..
If you have any questions you are welcome to ask.
BTW I'm growing with CFLs too you can take a look at my log if you want

GOOD LUCK

you cant tell from the pics but the lights are about 2 inches away, most of the stretching took place when i first started growing them with a desk lamp and the light from a window...

im going to wait a while before i put them in bigger pots because i don't want to stress them too much, but when i do i'll be sure to bury the stem.

as far as the soil being to hot goes, i don't have the money for recommended soil + nutes. so what doesn't kill you makes you stronger.. i hope.

ok 2 inch is good. but put your side lights above them for now.
btw transplanting if done correctly can cause nearly no stress to the plant.
and next time you use mircale soil flush it before planting in it, this will help abit

i actually moved them right after i took the pic. i can never transplant correctly, the root ball always falls apart for me. good call, i'll flush the soil next transplant, luckily im almost out of that stuff.

top view, then side view of each plant. i started to lst one of them, i probably didnt do it right, i was bored.

you know that when you transplant you have to water them first
then when you hold them between your fingers compress the soil with your hand.
this will stop the root ball from falling apart.
when LST you should pull your main cola down abit more then 90* that way the side shoots start growing(thats the whole point here init?)

yeah i watered them first, but i didnt compress them, thanks.

and for the lst, i know i should have waited to tie it down at the 3rd or 4th node, but im just an eager new grower :b. im going to continue to tie it down around the pot in a circle, couldnt wait to get it started.

is this adequate for scrog?

Haven't done scrog yet but I think it would work fine. I may try that on my next grow.

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My first grow!!

so i think i have my final setup. the plant are doing fine with the exception of 2 of them that have 2 yellow leaves each. the one in the center is doing really bad, thats fine though, i need more room... do plants this small have any thc content?... i've gotten high from smoking the leaves off a plant in veg in the past.

the new tops are finally starting to grow after the transplant.

more lsting

Dude I think you should germ some more seeds for that final setup you got so you will have some guys that are growing good and not strechy.
btw did you think about the light leaks during flowering? you cant allow any lights into the flowering room during their night time

light leaks wont be a problem, im kinda worried though, in that last pic you can see the leaf to the left that is yellow and brown all of the plants have this to some degree, some have bad yellowing and brown others only have slight yellowing and a speck of brown you can barely see, what could be causing this?

yellowing can be caused by many things.
post some pics in the plant problems forum.