Dwarf acara/smiling acara laying on its side

Recently i bought four dwarf acaras/smiling acaras and after i put them into the tank they went hiding as any new fish does.I made sure to properly 'prepare" them to water and temperature before adding them.Day later i see all of them alive but one started to act weird.He (the only male of this group) started to lay on the bottom,later even on his side and he wont start doing anything.He was escaping from the net and my hand but once i put him in a fish breeder he just lays on his side.Do you know what may be the problem? pH 6,5, temp 27C/80.5F, tank size 450l/80gal, amonia level 0, tank mates 6 angelfish juveniles, 8 dwarf corys, 2 electric blue rams and 5 otos

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