Yup I,d agree it,s going thru its natural process .Its normal to lose some lower leaves in flowering . Did you flush your pot at all ? I would that would clear up your soil troubles . Then I'd say if you havent ad any nutrient burn at your current dosage , go ahead and bump it up a notch give it 3 days to be sure its okay with that dose b4 adding any thing else to the soil besides a cal/mag supplement or a Liquid Karma type product.Your doing fine but yeah if your gonna grow 3ft+ plants they need 5g pots so they dont get rootbound .Also noticed your pot looks like the soil level is 2-3 inches down? So your probaly only in 2-2 1/2 gallons of soil.