1967 Dart GT- Brake lights and turn signals won't work when my marker lights are on but work fine when it's headlights on.

Hey all, I'm using 1157 LED bulbs in my tail lights. Weirdest thing, the brake lights and turn signals won't illuminate when my marker lights are on but work just fine when head lights are on or the headlight switch is pushed all the way in. Any suggestions?? I switched to an electronic flasher unit already and I swear they were working fine when I first got the bulbs. I did replace the tail lamps with new aftermarket ones so there is no corrosion or grounding issue I believe. Any help is appreciated all!!