Sick Butterfly, please help !!

[Rodney]

I had a similar issue with a lion fish was caused by a bacteria or parasite brought in by some used live rock I had bought. The fish were fine for weeks until a fluctuation in my tank caused an outbreak of ich and gave the bacteria/parisite it's in on my fish
I quarenteed the fish that survived and did a mala-fix treatment to the tank
I hope that's not the issue in your tank the survival percentage in mine was very low