I'm a Journeyman auto body and frame repair tech with over 37 years experience. The problem was a chemical reaction. Next time, use a catalyzed high build primer. You don't need a booth and fancy equipment because you can purchase RATTLE CAN CATALYZED PAINTS AND PRIMERS. They are not cheap, for rattle cans, around $25.00 each. You'll only need one. Four good coats with 20 min flash time between each, let cure overnight, block sand, carefully, THEN PAINT.