That fat contingency is the only way to survive.

Like @park.tara said, when they burn your hand.

Wait, did the primer can's instructions mention humidity levels? In my experience, the top coat is super picky, but the primer often has a humidity limit too, like below 85%. If it was humid enough to mess up the top coat, that primer might not have fully cured either, which could cause problems later.

Actually, pre-mixed mastic is fine for a backsplash. Thinset is overkill for small tile.

Honestly, that blue light thing can really help. My sister had a stubborn patch on her chin and tried a similar mask, not that exact brand but one with blue light. It took a few weeks but her skin cleared up way better than just creams alone. Makes sense if it's killing the bacteria. Just gotta be patient and stick with it.