Dan, the morality of a person or action is necessarily determined in context of moral standards. When your student says "Candide becomes immoral...", he or she is consciously or unconsciously applying some moral standard to Candide. (Of course I don't know what comes after the ellipsis, so I don't know whether or not the student clarifies ...). If Candide violates his own standards, his action is immoral and he becomes immoral in his own judgement. If Candide violates the student's standards, it is still appropriate for the student to claim that the act and the actor are immoral. But, ideally the student should clarify by what standard the action and actor are being judged.
Shorter and more to the point: a person can be judged immoral both in terms of external standards and his or her internal standards. And, clearly, an action can be judge immoral, again, against some standard.
Of course if the actor does not know that action is immoral or does not regard the action as immoral, by the actor's standard, the action is either moral or amoral.