lone frogspawn death

[Londre5000]

My favorite coral, a super radiant frogspawn looks like its on the way out. Tank has been up for 7 months, The coral was doing great and expanding for 3 months, then over the last week is retracted and already see parts are white and dying. The tank is full of 7 hammers, scoly's, couple SPS, numerous LPS and softys all which are fully extending all the time.

Parameters:
Nitrate: 5-10 (has been this way since tank started)
Phos: 0
CA: 450:
MG: 1200
Alk: 9.2

Have any of you just experience a coral death for no reason? Thoughts?

[Pond Boy]

Sometimes corals just wither away for no apparent reason...