I have literally had Kenya trees flourish in shady spots under arches in my tank as well as a few inches under 8 T5 bulbs. They have done well right in front of an MP40, and in areas with little flow. They have also been tolerant to high nitrates and phosphates, and even survived a crash many years ago where I lost nearly everything. I once bought a rock with a half inch branch on it, and it seriously went absolutely crazy in my tank and spread everywhere. So much so that I would have to cut it back at least every other month, and remove the little "seedlings" that would show up everywhere every couple of weeks.
Under the proper spectrum lighting, I have seen these corals thrive under just about any condition like I mentioned. That said, when I first bought my biocube, it was set up as a freshwater plant tank with a CF bulb similar to what you have. It may have been the exact same bulb. When I put cuttings of the Kenya Tree into it after it was cycled, they looked ok for a few weeks, and then withered down like yours looks. I changed the bulbs to the 50/50 CF bulbs, and it perked up within a week.
I honestly think it is your lighting. None of your fish would harm it, but I have seen or heard stories of a Peppermint Shrimp (or one of the lookalikes such as a camel) eating corals from softies, LPS, zoas, and SPS. There is some debate on whether they are actually eating it, or cleaning up when one is dying, but the possibility is still there.
I would first change your bulbs, and keep an eye on the shrimp. Most of the reports I have heard said they were caught eating a coral at night, so you may want to check with a flashlight after the sun is down.
