Big Kenya tree suddenly died!!!

[Subnautica]

The kenya trees in my tank occasionally close and will open up after a few days, but recently the biggest one in my tank suddenly died while the rest of the Kenya is doing fine. You can see the healthy one on the left literally just inches away from the dead one. What's happening? Looking at the dead one you can see some broken branches as well. Looks like they are melting day by day. Everything else in my tank is fine. Fish, corals and inverts are acting normal.

 

[Subnautica]

Bump

 

[rwreef]

Maybe something eating at it? ImE Kenys tree coral is like a weed and nothing kills it...so honestly not sure.