predatory micro brittle stars??

[novahobbies]

So I get home today and look in the tank. Photosynthetic gorgonians are looking great, pagoda cup and chalice are both showing some nice signs of growth with the MH light, zoas, shrooms, and rics are all open and thriving. Kenya tree is still shrunken in, but I'm pretty sure it's just sulking from the new light.
My pulsing Xenia, however, has shriveled down to a mere slime stump, and one of the branches is in fact drifting around in the current, having apparently let go of the substrate.
When I looked at it closer I noticed three small white micro brittle stars around the base of whatever's left of the Xenia.....for all the world they look like they're trying to digest it. Has anyone heard of this happening before?? The way I see it I'm looking at two possibilities: either they're actually attacking and eating the Xenia, or they're feeding off of necrotic tissue and something else is causing the degradation.
Either way, this makes Xenia colony number *3* that has disintegrated on me. :-/ I'm starting to feel like this is my version of Joe's Royal Gramma problem!!
I've tried to think of what I've done differently that may be causing this. I've started vodka dosing, still at very small amounts at the moment, and I've recently changed to a 20,000k bulb. Not sure if either would have done it, but I know that Xenia is very,....touchy....about changes in its environment.
Heck, even the GSP I used to have such a problem with is doing better! WTF gives with my ineptitude with such a supposedly "weedlike" coral?

 

[bang guy]

My guess is that the starfish are feeding on the dying tissue of the Xenia.
Xenia can be difficult to maintain when water quality is very high. They derive 100% of their phosphate and nitrogen from the water column so if there's nothing in the water they cannot grow even when receiving ideal lighting.

 

[novahobbies]

I kinda leaned on the dying tissue idea...if only to avoid the thought of trying to fish out however many microstars are in this tank. THAT wouldn't be fun!
Funny thing is....this is a seahorse tank. Meaning, there's always going to be SOME nitrate and phosphate in the tank because 'horses are a bit more messy than fish in their eating/venting habits. For instance, right now my Nitrates are at 5 ppm, and while my phosphate is unreadable, I have a small hair algae outbreak which is certainly bringing the phosphate level down.
As it stands, my Ammonia is 0, Nitrites are 0, calcium is 500, DkH was 8 (under API test) pH was 8.0. Ca seems a little high, and KH is a little on the low side, but a couple water changes should even those out.