You're effectively running a 2 week old plant. On a 7-4-4 plus extra cal and mag ontop of that. At 600ppm. Thats huge!Cut your calmag now!!! All of it. Your ph will stay stable longer.
Only give 200ppm of your 6-4-4!!!
Give it a good flush!
Wait a few hours. Then tell us if its improving.
Go by your runoff.
Let us know soon
Tim
Flush, mate. Flush
Good luck
Let us know!