Would a warship with three railgun turrets need armour because it would become a premium target?
Short answerProbably; concentrating that much firepower on one hull would make protection difficult to ignore.
NotesA ship carrying three railgun turrets would become a premium target. Armour would probably return as part of the design to protect that concentration of firepower. Navies may take time to accept the requirement while the weapons themselves mature. This remains a forecast rather than a defined warship program.