This morning I noticed my blue dwarf gourami, Oscar, is missing a piece from his tail fin. His colors are normal, he’s eating normally, and he’s still very active (taking a picture of him was difficult). His tankmate passed away the other day due to unrelated reasons and I’m worried he got Oscar sick as he died sometime in the night and was in the tank until I woke up and noticed. I treated the water and did a partial water replacement, assuming that was enough to keep Oscar safe and healthy. Please let me know if there’s more I should’ve done/should do as well as what you think might be the matter with Oscar. (Some extra information: he’s in a 5 gallon tank with a filter. Also the pictures are flipped for some reason, he’s swimming normally.)