Food carts and other businesses in Southeast Portland were badly damaged Tuesday morning in what investigators believe was an accidental propane tank explosion. The blast knocked out the windows of the nearby Crystal Guide, toppling display cases and overturning shelves at the shop, which sells crystals and jewelry. “I had a breakdown,” The Crystal Guide’s owner, Michelle Rademacher, 55, said of her reaction when arriving at the shop after the blast. The lot with the food-cart pod is strewn with twisted metal and various scorched items. I take care of anything and talk to the insurance, replace doors, replace the window, cook more food.”He added:“We will go on.”