Cap Losing Color

[RichardinMa]

Just over two weeks ago I placed a really nice fluorescent green cap into one of my tanks. It started out a glowing, neon green with brown polyps. PE has been very good ever since putting in into the tank. Within a couple days I noticed that the color was starting to lighten and figured it was due to the change in light. The tank I purchased it out of was lit by MH and the tank it is in now has 4x 39w T5. It is about 10" below the lights. Although the color continued to fade I was not too concerned as PE was still good but now I am seeing some very slight tissue pull back from the growing edge. PE is still very good and the polyps will retract if a push of water is blown on them and then come right back out again. If it were only a color change I would not be so concerned but this tissue loss had me worried. It does not seem to be progressing at this point but I am afraid it might begin again. I have other SPS in this tank- acros, seriatopora and they are not showing any tissues issues and all have good PE. Also, one week ago I added a couple other caps, including an orange/purple one, and there has been no color loss/change or tissue issues with those.

Parameters are:

T-79
Sal- 1.026
Ammonia- 0
Nitrite- 0
Nitrate- 0
Phos- 0
Calcium -400
Alk- 400
Mag- 1300

Any thoughts on why this one piece may be having trouble?

Here are a couple of photos to try to illustrate what is happening. The color accuracy is not great but it does show the lightening and tissue pull-back.

The day it was added:

Today:

 

[Felixc395]

If you can disregard light, I would check nutrients. How do you test phosphate and nitrate? Looks starved to me. Get some AA's goin in the tank or something, please, it's just hungry!

The only other option would be low K+... But I wouldn't worry about that as much as too little nutrients.

 

[RichardinMa]

I discovered it was nudis causing the problem. I have another thread about that.

Thanks