Sorry to hear the Tang died. Mine's doin' great today if that helps...
I can't say from experience, but based on what I've read in the past few days, Black ich is not "species specific". A parasite more common to a "geographical area". More common in some species,Tang's, and obviously more visible...
Don't know what to say about the white worms so I'll say nothin'... :? may be un-related because that would sound more of an internal parasite and that's just an additional problem... :shock:
Let me/us know how the next 2-6 weeks go. Best of luck from someone who needs it too...