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I doubt an anemone died from one day. An easy way to tell if it's dead, is to smell it out of the tank. Apparently, if it's dead, they smell awful. Also, can you take a better pic and tell us what type of anemone?
you need strong light for anemones. i would return the puffer and anything else that's not invert safe and the anemone might recover, depending on how much tissue it lost.
what kind of starfish? you might be losing that next.