SPS Frags losing skin and coloration

[CrunchyBananas]

I have a 60 gallon sps dominant tank that has been going downhill not long after making a move. Skin seems to be receding without any consistent patterning between frags (some lose patches on the base, some at the tip, some from coralite tips, some a combo of each.) These corals, rocks and fish all came from a successful 75 gallon system that was broken down and moved 2 months ago. The only strange thing I've noticed is all my snails froze up and died as if having a magnesium spike, but magnesium has stayed consistently around 1350, where it has always been.

The main change has been in lighting (switched from 4 t5 bulbs and 2 noopsyches to 2 hydra 52's and 1 hydra 52 HD). Other than that, parameters and dosing methods have remained consistent. Since the move, all acros have greened out and lost most if not all color, but they still all were growing (encrusting onto rocks and such) until about 2 weeks ago when skin started receding.

I've dipped and closely examined the unhealthiest seeming corals and have yet to see any sign of pests. Most of my larger colonies from my previous 75 gallon had been moved to a different tank, and they have all been flourishing, and no new additions have been added since the move. Therefore, I feel pests can be ruled out as any pests should be in both tanks. My alkalinity consumption has been dropping since coral health has seemed to decline, so my alkalinity has slowly climbed from low 8's to higher 8's over the fast 2-3 weeks. Below are my consistent parameters, what I am dosing, and pictures of the most noticeable tissues recession.

Dosing:
Brightwell Neonitro
Aquaforest 1,2,3+
Brightwell Coral Amino

Params:
Alk ~8.3 (trident/hanna checker)
Calc 430 (trident/salifert)
Mag 1350 (trident/salifert)
Nitrates 5-10 (salifert)
Phosphate .04 (Hanna)

Pics:

 

[Charlie’s Frags]

They look stressed and have started shutting down their metabolic processes. Did you check the par when you switched to the new lighting? How high are your hydras mounted? Any carbon dosing or gfo? Did you upgrade the skimmer too?

 

[CrunchyBananas]

They look stressed and have started shutting down their metabolic processes. Did you check the par when you switched to the new lighting? How high are your hydras mounted? Any carbon dosing or gfo? Did you upgrade the skimmer too?

That's a possibility I was thinking as well. I dont have a PAR meter but the lights dont hit above above 60% at peak intensity, they are mounted about 12" above the tank with their HMS mount. The corals exhibiting the tissue reduction are in the mid level of the tank, where as the top ones have full polyp extension. Other SPS frags have full polyp extension as well at all other levels in the tank (it is only ~12" deep IM SR-60).

I'm not doing any carbon dosing, but I just added a bag of higher grade carbon (if that even really means anything lol) with a little bit of GFO mixed in to try and pull potential contaminants out.

Lastly, I wasn't skimming on my last system, just a very large refugium was my filtration. On this tank I am using the IM ghost skimmer which is doing an okay job. it's an okay skimmer but the only one that can really fit in this tank.

The most bizarre thing is some other SPS are thriving (ASD rainbow Mille and JF weeble wobble) which are also at pretty much the same level in the tank as the stressed ones.

I have a water sample (pre adding carbon) to send in for an ICP analysis to try and gain some insight.