Strange Coral Death?

Hi all;

Had two thriving corals (bubble coral and button polyp coral) that were
doing fantastic. I decided to change my 20K Coral Life bulb last month.
The corals were doing fine until about 2 weeks since I changed the bulb.
The bubble coral closed and clamped up, and the button doesn't open the
usual way. The button is still alive and opening, except not as it used
to, but the bubble is dying; it's flesh literally rotting off the skeleton.

Yellow tang and chromies (spelling?) are thriving and doing fine, as are
the mushrooms and the rest of the shrimp, crabs et cetera.

Based on this, I can only assume it was a light problem; but if so, what
and why? Could the bulb be defective? I have no clue as to what happened.

All parameters are fine, except I have not done a water change in over 3
months. But then again, I've done that before and all inhabitants
appeared fine.

TIA,

Richard






--
"Dum Spiro, Spero."

As long as I breath, I hope.

Cicero (Ancient Rome)