6ph going in run off 7 how to fix this issue

600watt hps 77-80f 38-40rh pebble/coco 60/40 canna a+b coco cannazyme an biobloom had it spare but scared to mix all at low dosages shit me i put in 6ph water an runoff at the end was 7 what the fuckwhats making the ph go up just flushed them then added 456 ppm of nutes N???

http://www.growweedeasy.com/ph#how-much-pH-up-or-down

Read this. It addresses correcting runoff pH.