Why isn't Harry more concerned about Memory charms? He knows Hermione's been attacked, inside Hogwarts. For all he knows, every other character could be being manipulated by the enemy. His own memories could be false in arbitrary ways.

He should have gathered all his trusted allies and kept together. They can keep watch while each other sleep, and enlist the portraits to help. Give up on separate dorms. His enemies are playing to win; he needs to give up on his childish notion of 'going to school'.