Firstly, I would leaf tuck the best you can to allow the light you have to get down into those lowers.You can lightly defoliate over a course of time here and there to open them up a bit. As far as towards the bottom of the plant, if it doesn't look substantial and you want to focus the energy into the tops, you could lollipop a few nodes up. This would in turn increase air circulation up through the plants, especially with a tight canopy like that and when those buds start putting on weight.You could always do a partial harvest as well, snipping the main colas and letting those lower buds bulk up some when the time comes.