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.
stinkyattic Reviewed by stinkyattic on . Leaves Curling in soil S= Soil E-indoor E-soil E-specific medium (not sure of the brand) SCL-Added nothing to the soil SCLR-Unknown E-Water source(TAP) E-Source water pH (7.0) Rating: 5