They are looking sooo much better! Really nice green,
400ppm going in to 250ppm coming out seems odd, its very unusual for the ppms to be that low! You must have a really heavy feeder!
Are you watering through to where it comes out the bottom of your pot every watering?
But you need to shoot for 6.0-6.2 going in and stick with that, 6.4 is a little high... Its fine for one feeding but dont make a habit of it!
Are you watering everyday? Or at least keeping the coco completely moist?
6.4 going and 7.2 coming out is really high, not to mention really far between what you are feeding in!
I would feed them more then 400ppm, its only my opinion but when my plants get as big as yours are in your pics im feeding anywhere from 700-800ppm everyday!
But when i feed my plants (which are in coco as well, and i also use CANNA nutrients in the commerical grow)
The feed goes in at 700-800ppm and the run off comes out anywhere between 1000-1100ppm... My run off PH never varies away from 5.8-6.2
If its high then just water with lower ph, cause the coco will buffer it.
So if your run off is coming out 7.2 you need to do a good couple feedings at 5.8 to balance that out.
Dont forget the extra
calmag, you still have neon green tiger striping in the leaves, but they went from yellow green to neon green which is a great sign!
Just keep it up! Doing good!