Birdsnest Dying?

[Dos Ocho]

Hello all, seeing a problem with my Neon Green Birdsnest and wondering what you all think. i have noticed over the last week or so that the tips were turning white and looked skeletal. The polyps on the rest of the coral were not retracted and still had a bright green color. I thought it may be new growth, but now i see the white tips getting covered in brown stuff, perhaps algae. The rest of the coral seems fine. i have attached a pic of the coral from 6-18 and this morning to show the difference. i have 3 other SPS corals that seem fine, a pocillopora, pavona, and stylocoeniella. 

The most recent changes to the tank are; a toadstool leather coral added about a month ago. he was doing well but he has retracted his polyps and has not extended them for about 2 weeks. he's not drooping and i cannot see anything shedding from him, but i have read that leathers can release toxins that can harm other corals so maybe he is the cause? i have also added some BRS rubble rock to my sump. i am starting another tank soon and was going to let the rubble sit for a few weeks to help seed the new tank. i believe the addition of the dry rock has triggered a very slight diatom bloom. those are the only two changes that i can see causing this change in the birdsnest. i mainly have softies and LPS corals and all of them seem fine. Any ideas are much appreciated. My tank specs are below.

 

Biocube 29

~25lbs of rock, 1.5" sand bed

No skimmer, Marinepure balls, matrix media, and now some rubble rock in the sump

In Tank media basket with filter floss, BRS Carbon and GFO, and Purigen. Carbon changed every 2 weeks, GFO changed monthly

Ball of Chaeto in the 2nd chamber

4.5 gallon water changes every week using Red Sea Coral Pro Salt

 

 

PH - 7.8 - 8.0

Ammonia - 0

Nitrite - 0

Nitrate - 5 - 10 ppm, leaning more toward 5

Phosphate - 0 - .25, leaning lower than .25

 

I am still trying to get the hang of the Salifert test kits for the following info, so i guess take these numbers with a grain of salt

Alkalinity - 10.2 - 10.5

Magnesium - ~1400 ppm

Calcium - ~460 - 480 ppm

[Dos Ocho]

Sorry for not doing a bit more research ahead of time. i see there are several other posts about this and it looks to me like RTN or STN. So i guess my question now is, can i treat it? Should i clip the affected branches and see if it recovers? Should i cut my losses and get it out of the tank before it affects anything else? 

[Bingo1213]

It is RTN or STN which of course is just a symptom that can mean many different things.  I would would just watch it for a few days to see if it gets worse.  You may also try feeding it some phoyto.  It my experience that particular coral seems to thrive when fed.  Also I would not worry about the toadstool causing it.  It also should not hurt anything leaving the coral in the tank.  Look to see if you can see any parasites on the base of the coral.  Even try a flashlight in the dark if needed.  

 

[Dos Ocho]

Will do, thanks! 

[Clown79]

White tips is usually a sign of alk issues.

 

Rtn is the flesh peeling off.

 

While tips going white is a sign of parameter issues which can be the high phos or alk fluctuations.

White tips with algae is dead pieces.

 

It's important to be testing alk and ca for stony corals as fluctuations can cause them to go downhill quickly. They rely and use both to grow their skeleton.