SPS issues... again.

[doch]

I'm boggled. Every frag of SPS in my frag tank is doing great. Polyp extension like I've never had before. Colors could be better, but considering what I'm using for lights, no surprise. In my display however... SPS are dying like crazy. I've made 2 changes that I wonder about, but if you have any suggestions, please chime in. first, I switched from t5 to led. Switch was about 2 months ago... I think. They are tried and tested sols... Can't see this being the issue. Also, I now have a flag fin angel. I don't think he's been a problem, but I'm only watching the tank for so long each day. Any ideas? The 2 tanks are in the same system/water, so I can't see how it would be a chemistry issue, but who knows? Everything else in the display is doing great. Lps, zoas/palys, clams, etc... Just the SPS that seem to be mad.