Hi all, I set up a 20L tank with a group of 12 ember tetras about 6 months ago. They have done well since then and produced several offspring that have joined the main group. The embers are the only fish in there, but there is a colony of red cherry shrimp too. Planted setup with floaters, Anubias and subwassertang, normal parameters, lots of botanicals/moderate tannins.
Today, I noticed that the biggest one has an asymmetric white patch. Behavior/feeding is unaffected and the other fish are healthy. Only recent "husbandry change" is a brief temperature increase from 77F to 79, then down to 74 (heater issue, I have since raised it back to 78F to assist healing).
I am thinking fungal? Or less likely an abrasion/injury. Looking for thoughts before I begin treating further. Thanks in advance!