Getting white border in spot color channel selections

Super new to setting up spot colors and it's a little hard to find tutorials that aren't for textile screen printing.

I have files for some playing cards being printed with pantone cmyk coated. When I try to select a color range and make a channel, I'm getting white artifacting where colors should meet, I assume because they're somewhat detailed? Image attached as example.

How do I resolve this? Is this a matter of my base color actually needing to be printed first and extended underneath every other color, or maybe trapping, or maybe just expanding the selection?