RTN Birdsnest Help

[Craigdillman]

Wondering what i can do to prevent or whats going on with this RTN of a birdsnest colony. Noticed last night some white on the tips and one branch of the coral it was at night so didn't think much of it. Today my wife sent me pictures of the colony and i told her to take it off and by the time i got home over half of it was gone.

Nothing else effected, no changes but normal 25G WC 2 days ago and GFO change. possibly the other colony stung it but should cause whole colony death. Haven't added any new corals in over a month,

Paramaters

Calcium -380 bit on the low side
Mag - 1175
Alk-7.5-8
Phos- 0.09 hanna checker
Nitrates - undetectable
Salinity 1.025
temp 81

Nothing else changed kinda sucks this colony was over a year old grew from frag size











All this happened in less than 24 hours? any idea what happened ?


Thanks
Craig