Hi all, I need some suggestions when to switch to ...

No stretching at all.

I think you should have transferred to 12/12 another 2-3 weeks ago. in the last 3 weeks, your plant has just stretched. that is, nothing useful for this weeks happened to him. and now if you transfer it to bloom you will have a problem with very long branches, since they will stretch twice more. Switch to 12/12 now and use lst to each branches

she will double or even tripple in size but as you kept these low, i can say it will be a bit of a scary experience to see the stretch but it should stop just in time if you flip it around now. Hope this helps ! 🚀

I’d swich them to 12/12. One key point to switch is when you see that they have 3 floors of weed or 4 if you preffer. This mean that they are strong enough to go to flower. Maybe keep them 5 more days in veg so you can feel more confortable. I push them to go to flower at this stage because they grow asf when they are flowering. Some growers say to not to push because they get stressed and other stuff, but i do because i dont like them to be tall i want them to be fat. And also because of the space. I had one case that they were grew so much that were almost reaching the top of my ceiling. Had to take them out of the tend and give them their own room. Unless u want to wait for the little hairs to pop, but that can take until forever sometimes.

When you are switching to 12/12 the plants are generally have a 100% growth aka 2x the height she had when the 12/12 switch were done. It's a general value as indica can have almost no stretch but generally x1.5 and the sativas can be x3 or more. As you trained her she may stay short as the stretch will not only be a vertical one for you