Fourth week:
I start with some Easy Grow fertilizer. Half a bar for 3 liters of water. 1.5l x week.
As you can see I topped the sixth internode and I hope the branches stretch right now
Looks okay too me.. If it looked nitro heavy I'd say so trust me. So despite common belief and idea Nitrogen is not a very mobile nutrient once absorbed by the plant... If you think of how it uses nitrogen it would make sense that it wouldn't wanna get rid of it naturally. So most likely you still have some nitrogen coming in and the plant hasn't needed to transport from lower foliage to continue growing. It's really of no concern what so ever. If buds are nitro saturated for example it is nearly impossible to remove Nitro from the buds as the plant won't want to move the nitrogen around as it knows it's a required nutrient for growing and will leach from the leaves first.
Thanks to all the guys who answered me. Yes despite the flush, the leaves did not turn yellow and in fact during the vegetative I put only nitrogen. Today that the first week of FLush is over, I see that them have turned a little yellow.