Vietnamese Landrace Sativa monster

All going well, a few leaves have brown tips, not entirely sure what's going on, but will consult the bible. I have started giving them a small amount of nutrients, just to counter the falling nutrient levels in my soil, so perhaps I've been hasty and they are getting a bit much. With this grow I've decided to just let it grow natural, no trimming and topping etc, however, i have tried a few branches out just so they are getting a bit of light through the canopy. Switched to 12/12 yesterday, so this is the last veg post. I switched simply due to space worries, they are growing, well, like a weed. I think I've maybe timed it well, so hopefully they don't grow taller than i can support in my tent. Onto the flowering now.