When I read your first post, I also thought of spawning, but after your description, I'd say your tank was overstocked and probably the sight of a serious chemical battlefield, especially between the condi and any number of other cnidarians. Remember, this is a tiny tank, and so all the corals are in close proximity and much more likely to fight. When that happens in such a small amount of water, the toxicity will spike. The close proximity of stony corals and soft corals, especially, could trigger this.

Even under the best of circumstances, nano reefs are really touchy. Mine was a 10 with an external sump/refugium, and only really stabilized after I found corals that would happily share the same space. This turned out to be a couple of mushrooms, a monti (super low aggression), a capnella (one of the few soft corals with a low toxicity to stony corals) and an E quad anemone.

I could be wrong about all this, but it seems the most likely scenario. One other thing, in my nano, temp control was a *****. Do you know how much your temp fluctuated?