Duncan dying

[OpenOcean33]

So I have had this Duncan for a about 8 months. Started from one head and was growing great. I went overseas 2 months ago and when I came home and it looked bad and one head was dead. Over the past few weeks I noticed that the brown stuff growing on one of the dead heads. I don't believe its brown jelly disease from appearance but I looked under the microscope and it appears so be an algae and cyano mix ? It does not appear to be spreading but weird that cyano would grow their and no where else. Now today I looks and two of the heads are melting off of the skeleton barely hanging on but look normal healthy, just not attacked well. The only thing I have seen go wrong is a alk swings found out today. Ive had a busy week. However ive never had such a big alk swing. When I checked it was 6.3! I normal keep it around 7.7 and everything is happy there. I did do a water change and pre water change parameters included salinity 1.025, P- 0.07, N-8, Alk 6.3, Ca, 390, Mg, 1400. Any suggestions on what might be happening?

 

[reef lover]

The swing in parameters most likely was the cause and the cyano/algae just took advantage.

 

[Idoc]

Duncans are so picky... I've lost a few as well after they were doing great. My last one started melting due to stray voltage in the tank!