defoliating wont really help the buds down the bottom unless you are using powerful lights, you cant expect to penetrate that far without perhaps 1000W HID or equivalent with LED's.
Defoliating helps 100%, however you only need to remove the fan leaves that are restricting the majority of the other bud sites from receiving full light.
Just because your plants are bushy does not mean you need to turn them into stick insect, the plants still need leaves for growth etc if you dont have powerful lights dont try and trim the tree back please.
Just remember for your next grow then training your plants from an early age will give you not only a better yield but also a more manageable canopy, as you can see your main bud is getting max lights and the ones to the sides are receiving useless light.
We train our plants to make sure every bud site can receive USABLE light, a 600W light is best used around 7inches from the tops of your plant which also helps when the there are MULITPLE tops to your plant but all at the same height.