thats the nice thing on photoperiod, if the plant is slower , just let her grow 2 weeks longer. Then you have time to do more topping / supercropping on her to get her good in " shape" . i would give her another transplant into a 15 l pot. Shes in a 5l pot that is halfway filled. you cant expect more of her. Her growth of roots is limited here. eiher you switche her now , Or you give her much more soil in a bigger pot and train som more. I need for a trimming in the shape i want to see around 8 weeks.but then she has best conditions to get biiig flowers.