Hi, I recently spotted my fish with some grey-white smudges on its back and was wondering if it was ich or some disease. It seems to be more lethargic than usual. It is a figure 8 puffer (I keep it at a salinity of between 1.004-1.005) and it used to be living with another puffer that I discovered was dead two days after. I am not sure if it got infected by the bacteria because of the death of the fish. I have had both fishes for around a year now, and this is the first time that it seems to be sick. Can anyone tell what disease this is, and how to treat it? I haven’t introduced any new fish at all and I do a full water change at least every 2 weeks. I believe it is a 15 gallon tank which is enough for a f8 puffer. Thank you so much!