Yes, some plants/genetics have rather strange flowering time lines. Some will develop at a steady pace, others will start really slowly then finish quickly and others will grow in "spurts", meaning they grow, go slow, grow again then slow down again. Some Sativas take ages to get going then grow slowly and finish like they are in some sort of flowering race. Generally Indica or Indica dominant plants like your Northern Lights, grow more or less steadily, throughout their flowering cycle. I would suggest trying to gently bend the main stem over, a little bit each day until it is nearly level with the rest of the growing tops. This way you can lower the light and provide a much more even light distribution. At the moment, by having the light above the main stem, those lower branches are receiving vastly diminished light in comparison to the taller main stem. Your plant will flower a lot quicker once the light has been lowered, due to the increased light intensity the entire plant will then receive. Your main stem will cope with being bent down, cannabis is a remarkably resilient plant. In nature things like branches from other tree can fall on cannabis plants and the plant will "sort itself out". Doing some training now will present less problems than when the plant is further advanced in flowering. Just do the bending down/training, slowly, say to 45 degree angle today, then a further 20 degrees tomorrow and the final bending down the next day, until the main stem is almost parallel with the ground. If the main stem is proving too stiff, do this bending over 4-5 days and in lower increments. Even if the worst happens and the main stem snaps, your plant will heal itself and continue growing, but you will have to tie the main stem, above the break, to something like a bamboo stake or a loop of string from the roof of your tent. If it does snap, do not place any tape/bandage around the break as this only encourages fungus/bacteria to grow. Just leave it exposed to the open air and the smarty pants cannabis plant will heal itself and continue flowering. Obviously you should try and avoid this from happening though. Once the main stem has been bent over, you can direct the flowers growing on the main stem into new positions, so that they are once again growing upwards toward the light. This may take a few days until they are also "re-trained" and staying in position.
At this stage, seeing as you have a strict time deadline, trying to even up the height of your plants canopy is your only real option into speeding up its flowering rate. I would also suggest skipping a couple of feeds with "bloom" type nutrients and giving her an increase of "grow" nutrients for a couple of feeds, to try and green her up a bit as she looks a bit pale for this early stage of flowering. This will also give her a bit more of a boost to speed up the flowering. At this early stage in flowering, nitrogen is still an important need. Hope this helps.... Organoman.
PS - For your next grow, may I suggest another breeder instead of the one you are now growing, their genetics seem to be somewhat variable and unstable, with a recurring theme of mixed results, judging by how often questions about their plants come up in this forum. 😨 Good luck and happy harvest!!