The other half were probably just dusty.

Wait, do disco lights mess with the laser's level or the distance finder?

Remember my friend who had super oily hair no matter what she tried? She started doing exactly what @wright.dakota said, washing with cool water from the get-go. She said it felt weird for a week, but her scalp totally calmed down. She used to need dry shampoo by noon, now she can go two days without washing. The cold final rinse still makes her ends shiny, but the cool wash changed everything for her hair.