Possible issues with Pura Phoslock?

[Fedcopmike]

Switched phosphate media in my reactor last week, then I lost a 6" Derasa and a 3" Crocea, no other changes, also running carbon reactor after phosphate reactor - inline.
Water Parameters: 72 Bow
Temp 78
PH 7.8
Calcium 550
Mag 1450
Phosphates .04
Nitrates/amm 0.0
Alkalinity 11
Lights - 2 250w 10k MH/48" Actinic VHO
Any ideas?