Odd Acan Behavior?

[Jooak9]

Hello everyone,

I am writing for some advice on my 1 of 3 small Acan frags that has been doing super awesome until today. Overnight it turned from awesome to the picture I am including next.

Of note - my other 2 Acan frags/small colony is fine and looks as usual - as you may notice a few inches over in the pictures.

Thanks for the help/advice? Is this what happens potentially when they grow another head? Could an unknown pest do this?  There is a small dark spot I noticed and you may notice in the image as well.

Thanks and talk later - Josh

[Jooak9]

Other “things” of note.  I did check the following parameters just to make sure nothing was weird.

Salinity. 1.024 or so - usual for my tank
Alk 8.8
Phosphates 0.04.

Yesterday included a routine 2 gallon per week water change.
And a routine monthly or bi monthly carbon / gfo mixed bag change.  I don’t run much of it though - 3to 4 tablespoons of carbon to 1 to 2 tablespoons gfo per bag and have two bags in the HOB.  Fairly standard practice for my tank for a while now.

Most puzzling is all of the other corals look as usual with the exception of this particular Acan???