Is DT crashing?

[Ferrell]

Only been at this a year with 75 gallon mixed reef. Have good success with most LPS. Battling Aiptasia outbreak and have been exposing them in their crevices. About a week ago, the chalice which I’ve had since March and was about silver dollar size started bleaching around the edges, then overtook one mouth. So I fragged out the bad and placed it back in tank but now it’s almost bleached out. Other chalice doing great. This morning I wake up and the 6 headed Duncan is jelly. I immediately pulled out. Also have anothe mycedium that is begun to bleach. What course of action should be taken?
I cleaned out my skimmer and return pump during normal bi weekly water change.
Parameters are nitrate 8, phosphate 0.09-0.13, Alk 8.6,ph 8.1-8.3
Run carbon and GFO in bay as needed
Only new additions were yellow tang and kole tang on dec 1 after 40 days qt
Zoas acans lepta mushrooms gsp hammers leathers platys lobo all look good
Do i need to remove/discard affected/infected?

 

[Ferrell]

Oh I did yank the Duncan skeleton out as soon as I saw it melted. Also have few easy sps that are doing good and encrustion. Poccillipora, green slimer and a couple others

 

[uutank]

Did you had any recent alk swing? Parameters look okay. What’s your calcium and magnesium? Also do you dip your corals?

 

[Ferrell]

Have not had Alk swing that I saw. I test every other day @ 13:00 and generally 8.4-8.6. Calcium 430-440, mag stays around 1450 (never added any)
Only changes: upped sock change schedule from 4 to every 3 days, did a sump clean as part of my 6 month maintenance (cleaned skimmer, return pump and chambers of detritus and junk) during 15% WC, added two tangs from qt of 40 days and got a WXM which I programmed flow similar to what I was running but with a nightly nutrient transport programmed in
Yes dip corals in Coral RX. The ones that died were not recent additions.
Lost: 6 month old chalice which had doubled, 6 month Duncan, JF hydnophra, 1 month green slimer this morning rtn. All removed.
LPS acans hammers and platys look great+ others. Just baffled and nervously watching close

 

[uutank]

Man you lost you slimer this morning? dang. Yesterday it was fine I guess. Your params are right certainly.
Maybe some sort of infection on your corals(can be bacterial, fungal,parasitic), though you dip, but try iodine dip.
But I would like to hear others too on your curious case before making any judgement.