gill curl and cannot sink arowana

[Aro77]

hi , have this one red that cant sink , abit of its body is above water. i got some epsom salt and dose approximately half teaspoon for every 40L the aro seemed to be improving. today after 2 days since last dosage. i did a 20% water changed and added another round of epsom salt and very surprisingly , i just went to see the aro , it's Soft GILLS have curled , also has been having mild cloudy eyes for a few days already.

also had 1 small indo tiger in there now the indo tiger has sank to the bottom of the tank and doesn't seem to be swimming around. can any bros advice what should i do from here. im pretty much out of ideas