When to switch to 12/12

My white widow fem are 7 weeks old. I topped the plants and am trying LST. when is it best to switch to 12/12 light and how long to harvest after i do. The plants do not look like they are big enough yet. I may have stunted their growth by pruning

It’s all about managing the space that you have to work with and take into consideration after the flip plants can double sometimes triple in size. That being said you can flip anytime you like .Hope that helps


7 weeks should good time wise