Hello
I just finished my first indoor grow, so I am not sure how others feel about it, but I try to refrain from doing any high-stress training on my plants after they start showing pistils. I wouldn't want to over-stress them and hermie them. (Again, 99% of my growing experience comes from outdoors, where height is normally not an issue. So my opinion on that may be invalid.)
I don't see any pistils on your plants yet, so you should be ok tying them over as long as you are gentle and dont go crazy super-cropping them if you need to keep them a little shorter. I definitely wouldn't top them this late if that was the direction you were heading.
Looking at the height of them, you will probably be looking at another 6" or so of stretch before they start filling in instead of going vertical.
A few quick questions on that note though. Like I said, I'm not seeing any pistils on your plants yet. Is that 2 weeks of flower? Or 2 weeks since you swapped to 12/12? There's usually a good one to two week transition period before they start proper flowering.
And what type of lights are you using? Just that one CFL, or is that just supplemental?
Your plants look really healthy though, very nice I would say