If you have corals or anemones in the tank there is bound to be some sort of chemical warfare. Anemones are notorious for releasing nematocysts in the water, especially one that is always on the move. Running carbon and aggressive skimming will usually tank care of that.
, the anemone should not wander. The tank conditions may be excellent based on test results but that is not the only thing to look at when dealing with anemones. As Sixline mentioned, water flow and light are paramount. If chemical warfare was the issue, it's fixed easily enough.