Odd bleaching - help appreciated

[impur]

Hey everyone, i'm a little stumped on what is happening in my tank to specifically some of my SPS corals. My pH has been on the low side, around 7.8 at night and 8.0 daytime. I'm not overly concerned about that, but now i've got some odd bleaching on 2 of my corals. One is an awesome green slimer i got from Mike, the other a nice purple w/ green polyps. I just noticed the bleached spot on the purple one, the slimer had been down on the sand and i have since moved it up a bit in hopes that it was needing more light. But the purple is a mystery to me why its happening. The whole coral looks fine otherwise. Here are the pics. I just checked my levels 5 minutes ago as well and all is fine there.

temp 79.5
pH 7.9
SG 1.025
alk 8dKH
calcium 450ppm
phos 0ppm
nitrates 0ppm
nitrites 0ppm
ammonia 0ppm

slimer yesterday

slimer this morning

 

[Travis]

I hope I'm wrong, but the first coral you posted appears to be showing "tell-tale" signs of acro eating FW damage. But it could just be an STN issue. I would check it at night with a flashlight and look for AEFW's. Probably the easiest way to see them is by taking the coral out of the water and letting it dry out for a few minutes. Then the coral will appear dry but if there are ay FW's they will look wet.

 

[impur]

I sure hope that is not the case. I'll try letting the coral dry a bit tomorrow

 

[impur]

Well the damage on the slimer is still progressing, slow now thats its in more flow. The purple/green polyps coral is on the sand right by the glass so i can watch it. The bleaching is not getting any worse on that one. I think i might pull the slimer and dip it in some lugols just to be sure there are no AEFW.

 

[Travis]

Let it soak a tad longer than usual in lugols. Then lightly baste the coral with a turkey baster or small powerhead. If there are any FW's, they will fly off when you do this. I would do the basting in another container with fresh tank water and a white bottom as it will make it easier to inspect for FW's in the container. Good Luck.

 

[impur]

Thanks Travis.