The question really doesn't have anything to do with how old the plant is. Generally speaking as long as a plant is at least about 3-5 weeks long its ready to flower just as long as the environment allows for it (around atleast 12 hours of darkness usually). How long its going to flower is strain dependent; indicas are usually around 7-9 weeks and sativas go from about to 10-16 usually.

The yellowing/browning can easily be from over fert, what and how are you feeding it and sometimes when new leaves tips brown or yellow it can be a nutrient deficiency but that's more uncommon. Feed them a little later then you usually would and give a really good watering in between and you should be good.

If you want to make it bushier and top it go ahead but be careful and make sure everything is sterile. When you actually cut it be efficient about it and don't hesitate when you go for the cut. If its you first time doing it I'd really only make a few cuts at most you don't want to shock the plant too badly.
Smoketobehappy Reviewed by Smoketobehappy on . New Grower (problems + Questions) Hi, my problem is that the new growing leaves have brown tips, this is the first time it has happend, i dont know what im doing wrong. I also dont know if to cut some big leaves off to let more sun light to the new branches. any answers very much appretiated, thanks :hippy: Rating: 5