Why are 2 Euphyllia receding?

[kwall737]

So just within the last few days, I’ve noticed 2 of my corals receding or dying off and i have no idea why. 1st is a frogspawn that I’ve had for over a year, and the 2nd is a hammer I’ve had for 3 weeks. Tank is a Waterbox 130 that I’ve had running for almost a year and a half, has 14 fish and mostly lps (hammers, torch and frogspawn) with a few softies and running 2 XR-15 Blues at AB+ lighting schedule for 10 hrs a day with the following params - temp 78, salinity 1.026, alk 9, calc 470, nitrate 15 (have gotten it down from over 40 in the last 2 months) and ph 8.1 - 8.3. The corals in question have not touched other coral nearby, and doubt any fish i have are bothering them either. All other coral in the tank seems to be thriving. Anyone know what could be going or what i could do to help this from happening to others?? Thanks!

 

[rooneyj889]

Might wanna check magnesium. From what i understand they like mag and suck it out of the water

 

[zuri]

get the this one on the rockwork where it can expand without touching the rock get some glue. you don't want to wedge your corals into the rockwork the frogspawn looks like it has heads in the dark aswell. the wall is most likely on its way out