Hi, Mats!
Well, I actually had tested the shop's water before moving the fish to my tank, and except for the ammonia that was a little high in the store's sample, the rest was pretty much close to my water parameters, like pH. I did acclimatised it too. I kept slowly adding my water to the container where it was with store water for over an hour. Maybe it wasnt enough though

I added a fungus clear to the tank just in case it was some kind of disease and was spread to the other fish.
Also, I bought 2 of these guys as "emerald cories" (brocchis splendens), but they are not as green as my first emerald cory. Can they be more brownish?