I've had a Heniochus butterfly for about 5 months now. he used to eat like a pig but now shows no interest in food, and I've tried them all. I also lost a Lemon Peel Angel 3 weeks ago. He stopped eating and died about 6 days later. My water parameters are good. NH3/4=0, Nitrites =0, Nitrates=15, PH=8.1, Temp=78.1 and SG=1.023. It's a 110 Gal tank, with plenty of live rock. Up and running for 14 months. No obvious signs of disease on any fish including the lemon peel and the Heniochus. Any help would be appreciated. Thanks in advance!!