This is not HLLE but looks more than Lymphocystis and would make sense as to results after FW baths.
Lympho is viral and generally associated with water quality and diet.
Verify your tank readings and if you are using API test kits, you may likely be getting false readings with belief they are spot on when they are actually higher than you are seeing. With good water quality, lympho will fall off fish.
As for diet, feed at minimum:
Spirulina brine shrimp
Nori seaweed basted with garlic extract
LRS Herbivore diet
Formula 2 flake and frozen
Hikari Marine cuisine
Hikari Mega marine algae
Mysis shrimp
small plankton
Add selcon vitamins to the food 2-3X per week and garlic extract on alternating days for immunity system health and overall stamina