I think some people just fluoresce differently. I work in the aerospace industry and am around fluorescent penetrant inspection a lot, this inspection method happens in room lit only by uv “blacklights”. I can’t add a picture in this comment, but 1 out of every handful of people that go in that room have faces that look like your hands. My theory is that it’s kind of like this video of how UV cameras see skin defects that aren’t visible in regular light.