Hammer with Male Pattern Baldness

[sleepydoc]

I got a green hammer coral about 4-5 weeks ago and one of the heads has developed a bald spot. On it. The other head appears to be doing ok, and there are new buds developing on the main stem, so I think it's healthy otherwise.

There was a period where the Alk dropped to around 7 before I caught it, otherwise my params are as below. Any ideas as to what's going on?

KH 9.2 Mg 1300 Ca 390 pH 8.2 SG 1.026
NH4 0 NH2~0 NH3 2.5-5

 

[Mental1]

FWIW, Hammer is an LPS coral and not a soft coral. I can't tell from the picture but it looks like it might be brown jelly. If it looks brown, it will spread and kill the rest of the heads so cut it off immediately. I also try to use a turkey baster to suck up the brown jelly before moving it so that the brown jelly doesn't float in the tank. It will affect other corals.

 

[sleepydoc]

Oops! Sorry! I'll re-post over on the LPS forum.