I share your pain. I've been getting random STN all summer and I have no idea why. I try here for answers and you get asked the basics that you've already run through a million times before deciding to post for help. Makes you want to bang your head against the tank until things work.
One comment I may make on the Ultralith system: It is a low nutrient system. Check out Fragd'it's blog about ultra-low nutrient systems. Sure it makes the corals look pretty but it also makes them more susceptable to bad things happening. Personally, I feel a little skeptical as to how "good" these systems are for your tank. I'm not criticizing or anything, just sayin' the low nutrient system itself (or the transition to it) might be the cause.
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