Hermione realized as he walked away, Percy was having the nightmares. The way he spoke about it, the sound of his voice, there was no denying it, and then she saw the spot on his neck, and she put a hand to her mouth and grabbed Ron's hand before she spoke, gathering her thoughts and proceeding cautiously.
"Percy," she said quietly. "On your neck, you... You have a black spot on you're neck. You're having the nightmares," she said rather than asked. After their discussion at the DA meeting last night, the spot was a connection to the nightmares. "Percy, part of the reason I'm going to the DoM is to figure out what the spots mean, why they're connected to the dreams. I'll keep you in the know about what I find out, we'll figure this out, one way or another."