My stars are falling

[cgr]

A couple of days ago I asked for help in trying to figure out what is happening to my starfish. One of my two sand sifting stars was missing two of its arms and the next day it was dead. The other sand sifter is ok and has all its arms. Yesterday, I noticed a dark moving glob in the bottom of my tank. It was my brittle star which lost all its arms and is barely alive in my QT. I have another brittle which is fine. I cannot find anything that could be causing this cosmic devastation of the stars in my tank. I don't think I have a mantis shrimp.
120 Gal FOWLR
1 Yellow tang
1 Blue tang
1 Sailfin tang
3 chromis
1 cleaner wrass
1 tomato clown
1 sleeper gobie
1 skunk cleaner shrimp
1 coral banded shrimp
2 peppermint shrimp
1 sandsifter star
1 brittle star
snails, blue and red legged hermits
Ammonia 0, Nitrites 0, Nitrates 0, PH 8.2, Salinity 1.023

 

[clarkiiboi]

The only thing I do know is acclimation is the key......how did you do it, and how long? Hopefully this will bump ya for a better answer.

 

[ophiura]

Yes, how long have you had them and how did you acclimate (if they were added in the last month)?
Did you recently do any water changes?
Do you feed the brittlestars anything?
Your salinity is a touch low, IMO.
Sand sifter stars are notorious for dying at 9-12 months, of starvation, and what you describe is typical for this.
However, with a brittlestar involved it seems like it might be related to any sudden shift in pH, alk, specific gravity or temperature.
The loss of legs like this is often associated with shock, and not predation. Predatory attacks result in the loss of one or two arms, typically, in brittlestars.
Unfortunately, one of the worst things to do is to move it to another system, as this is highly stressful (especially if they are not acclimated for many hours). The best thing to do is to leave them in a stable system with params in the ideal range.