The spotlight effects are NPA (non-pixel art) - you're using opacity effects and soft brushes (automatic anti-aliasing). Both of these create a lot of redundant colours outside of your control. The speakers and bass drum also seem to be soft-brushed in.
Even though the rest of the piece is pixel art, PJ doesn't allow effects like that because the site wants to keep its focus entirely on pixel art.
You're right. Well spotted. I'll redraw those parts by hand and re-submit.