Torch Coral split, now one head is dying?

[Ewait]

Hey all,

I've had this torch for quite a while now and about 9 months ago it split. No signs of it being unhealthy during and post split, so I just kept my regular care routine for it the same.
Now about a month ago, one of the heads stopped inflating. I asked my local lfs staff about it and they said that their torches do that sometimes, but will always bounce back after a few weeks. Unfortunately now things have gotten worse and I fear that the one head may be dying. Any ideas as to why this might be happening to one head and not the other?

 

[Ewait]

I have also just noticed a tiny bit of what looks like green hair algae (?) growing up against the torch. Could this be causing my issue?