In my opinion your plants are a little small to be at 4 weeks. What light intensity and light you running? What are your temps and rh like? What ec are you feeding? When u say gh nute line are you talking trio?
I would find it difficult to dial in an environment with autos. IME autos(mephisto, mendo20) seem to like less nutes and less par. They also grow fast so if that's really 4 weeks she'll be flowering soon.