That's some healthy growth!Your defoliation payed off well. Also, you really don't have to control your tank pH THAT closely, it will naturally change as your plant takes up nutrients, but you can let it get to about 7.5 before you add some lower pH water to your tank to bring it back down.
Also, if your plant is about a 1/3 of the height to the bottom of your lights, your should switch to flower, otherwise you won't have enough room to raise your lights before they finish stretching I can't really tell from the angle that your picture was taken from, but you may be getting close.