Tang issue

[surge19us]

My yellow tang developed this round spot on its face about two or three months ago. I originally thought it got stung by the torch or frogspawn. It is only the one spot and hasn't gotten any better or any worse. Any ideas?

 

[billsreef]

It appears to the beginnings of head and lateral line erosion (HLLE). What are you feeding the tang?

 

[surge19us]

PE Mysis, Rods food, Sea veggies. Vita Chem, It is only on one sid and perfectly round. I don't think its HLLE, The other side of his face is normal. As a precaution I started feeding more garlic and sea veggies. It hasn't changed in 3 months. Thats why I originally thought it was a coral sting. Its like it lost just those scales and actually a few seemed to have returned in the very middle.