Hermit , post a picture so can have a look at what's going on ,
Sometimes they sulk for no reason or shift in parameters,usually very hardy , I've not known anyone to lose one personally but that doesn't mean someone has.
I've not fragged mine yet as sorting out decor in the tank at the moment so not sure where it will go.
Easy to do though ,
Wave you're hand gently over the top till all the feelers /tentacles/hairs whatever you want to call them are all closed up and it looks like a plain piece of rubber ,
You can do this out of the tank if you can if not then you can do it in the tank.
Use clean Sharp scissors and cut off a size piece you want to use as a new frag. Try to make sure that when you cut it with scissors it's done in one cut not two less stress that way
And then you can fix the new frag you have made to a suitable piece of rock.
Here's a picture of my toady that I will eventually take a frag from when I've sorted out a bit more of decor and worked out where it will go.
Tip when you do it is to relax , don't panic ,and have everything you need laid out ready to fix new frag to,
Good luck I'm sure you will be ok ,
Send a picture of yours before you frag it though / here's mine as mentioned that I will be taking a frag from .