I think there are clear pictures on the web showing the differences btw brown jelly diseases vs Brown filament discharge. I’ve recently gotten few torches and one had the brown stringy stuff coming out and didn’t look good for few days. I just used activated carbon but I can tell it wasn’t brown jelly diseases because that one seems to cover the coral instead of discharge?
And I am not sure if it was caused by vermitid snails. Maybe you have the ones that are really big?!? But they usually irritate the corals and not really kill them. If you have issues with vermitid snails casting web, you should clear up your water column from having particles flowing around. And corals do die for no reason, if your other corals are looks good…. Try to save it. I would cut the branches from healthy one. Looks to be two branches?