chalices dying help

[mikea213]

So over the last few weeks my chalices have been burning out starts at the edge and moves in and its only been my expensive ones so far go figure all the tank levels are normal. Any ideas? Nothings been added or changed other that gfo but it started before that.

 

[mikea213]

Tank is 180g
2 mp40
2 EVO 250w LEDs
Calcium reactor
Ev-240 skimmer
Phos reactor running BRS GFO

Temp 78
Salinity 1.025
Ph 8.3
Mag 1375
Nitrite 0
Nitrate 20
Alk 4 mlq
Calcium 420
Phos .14ppm