Off rip you need to lose the reflector on the back light, its sending light down when there aint need for it when the light can be going to the top buds, it would be useful if that reflector was directly over the top of the plant! Some of the other reflectors need to be repositioned to give better light penetration. That takes care of your lighting issue!
Now with the yellowing your correct with adding a little bone meal for n, the plants still require n in flowering, just not as much as in veging, each strain is different in their needs, yours might require a little bit more than some!
Make the lighting change and youll gain more dense buds and heavier buds! You have a sativa take it into at least 10 weeks in flower and even better yet 12 for maximum weight!
Good luck Dude!