Bumping this for you
A pic in less blue focusing on the brown stuff would be a big help.
That said,brown jelly disease normally kills superfast and spreads even faster. So if it is bjd, it is being quite slow. And if it is, then you would want to cutoff the infected head and trash it, dip the one that hasn't shown signs of bjd, and simultaneously do a major water change (like 75- 80%, or more if possible) in your tank to get as much of the possibly tainted water out as possible. And run carbon.
All that said, even if it is BJD it could always be some other infection. Or just something about the parameters that the coral didn't take to.