Just to give an update that my Utter Chaos is vanished. Literally. It was melting away and now it is completely gone. It was 1.5 polyp frag. I don't understand why. Everything else in the tank is healthy. The only think that I can think of was at one point I ran out of Trident reagent B and C. The Alk test always came back the same amount of number consecutively and this has never happened before. So at the time, I either did not dose Alk or dose too little or too much. I dose manually for now. Once I replaced the reagent B and C, I started to get the "normal" Alk test results. So it looks like with empty reagent B and C, it can mess up Alk test. At least that was my experience.
Anyway, is it possible that Alk swing can cause utter chaos zoa to melt away and then disappeared? Why my other corals were not effected at all?