if your getting 1200 ppm runoff,you need to keep flushing,those numbers coming out should be close to whats going in,you have a salt buildup thats why every thing is locking up,plant dont know what to do,you can continue to foiler the cal mag if you insist,me personally think your wasting time,flush the plant with 6.0 to 6.2 ph water .flush ,when you get close to either or the ph being right ,then flush a couple more jugs with your ph and nutrient solution at 600ppm to finalize the flush,check your runoff mate,each time to see were you stand ,you could run 20 gal of water threw there before you get it right,but plant is yellow from salt buildup,even transplanting the plant into new soil isnt gonna help unless you transplant nothing but roots ,all old coco off plant,and at this state you probally gonna kill it