a 400watt bulb is perfect for your place.
As far as your plant layout, i would recommend you split the box into 2 vertical boxes. This is good idea for a few reasons:
-to grow your plants 6 feet tall in that narrow of a box could be a problem. You could probably fit 3 plants in there
-If you...
are you flushing the old ferts out before you pour new ones in? If you water with 300ppm and they only use 100, and then you add another 400 you raise it up to 600. Make sure you flush before adding new ones to prevent this
just invest in a 30 dollar PPM meter on ebay and then you wont have to figure anything out. Its way easier when you can accurately measure your nutrients
It shows no sign of burning from over fertilization, it looks like its been overwatered. Dont water again until the soil shrinks in from the side of the cup
PS: Make sure there is lots of drainage on that cup!
This is a nitrogen deficiency
https://www.rollitup.org/members/beefsupreme-158755/albums/deficiencys-7853/76528-early-stage-if-nitrogen-deficiency/
2nd thing, plants will never/rarely show nitrogen deficiencies in flower because they dont use much nitrogen at all. They look healthy to me...