Looking really good mate. Seems like youve got your feeds right.
I would say that mars 300 is a little under powered for a large plant.
As dudeski said you can take off some fan leaves that are blocking the lower parts.
Or do some training- gently spread out the outer branches to let more light down there.
Just be careful- training is better done when plants are younger, the stems harden up later in the grow and can snap easier!
Flexi pipe cleaners are an easy way to keep an easy canopy
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An even canopy gives an equal amount of light to the plant making more large colas