It sounds like you should switch to Flower mode ASAP. To a 12/12 light scheduel. For the last two rounds I've done a three day total dark period (as recomended by Stinky) and I believe it has helped for the girls to bud faster.

As for clones: The basic advice is to reduce the nitrogen (which you should do to switch to Flower phase anyhow), take clones, and then to let them recover before changing to 12/12 for 10-14 days.

I have had fine success taking the clones/ pruning and going almost directly to flowering/ dark phase. I have also had sucess taking clones after the plants are into Flowering. I guess it depends on how big the plant is and what your goals. For example if you were topping or doing FLIM in order to get more growth areas to increase bud sights, you'd want to let things veg longer. Also, do not cut more than 1/3 of the plant....and when I've had sucess, and I say pruning...most of what I've cut and turned to clones are from the lower "sucker" like branches that will not produce much bud or thinnning of the thick growth in the middle ect. Not huge mainstem chunks...