From the the pictures, the anemone is definitly distressed. For an example, the tentacle lenth and disappearnce of the verrucae/fading is not normal seen in an established mertensii.
What is the alk, CA, and Mg levels? Again, if it was my anemone, I would get some new test kids and double check just to be sure.
I have never found an anemone safe butterfly, particularly in a same tank with an already distressed anemone.
I am not sure of the lighting issue because mertensii mostly from deep water and I have never seen mertensii in less then 30 feet deep, even in extreme low tide. A chronic insufficient lighting will produced browning not fading of its coloration. Bleaching, fading of the oral disc/tentacles, and verrucase mostly, happens in an acute situation for this specie. Just my personal observation, good luck.
What is the alk, CA, and Mg levels? Again, if it was my anemone, I would get some new test kids and double check just to be sure.
I have never found an anemone safe butterfly, particularly in a same tank with an already distressed anemone.
I am not sure of the lighting issue because mertensii mostly from deep water and I have never seen mertensii in less then 30 feet deep, even in extreme low tide. A chronic insufficient lighting will produced browning not fading of its coloration. Bleaching, fading of the oral disc/tentacles, and verrucase mostly, happens in an acute situation for this specie. Just my personal observation, good luck.