Yeah. Your plants are pot bound. PPP will outgrow its pot REAL fast. You need a gallon of medium for each foot of main stem. Also make sure your air flow is enough to supply ample CO2 to a horde of monsters.

That is neither overfert nor Mg deficiency. I don't see any 'leaves curling up and dying'... and the first sign of Mg def is BOLD even stripes on the leaves.