hey ez.. yeh mate i just ran some 6.0 thru the girls.. lke u said
classic mag lockout..
need to keep that ph pen calibrated..
What happened was i was getting high pH run-off readings so i dropped my pH drastically to try to balance the run-off, THEN i was to find out that pH run-off in coco is moot point, it only matters what goes in.. So dropping the pH so much was the beginning of my trouble..
Then i was watering pH 5.8, which was really 5.5 cos my pen was bunk so mag was getting locked out still!, and the shit hit the pan

Add to that lazy habits like not standing my water out regularly and not letting my nute mix settle and double checking..
Like Alf Stewart would say 'let that be a lesson to ya, ya flamin' mongrel