Cover the guajillo chiles with hot water and soak until pliable, about 15 minutes. Drain. Blend with tomatoes, onion, garlic, and 1 cup of the stock until smooth; strain if desired.
Heat oil in a soup pot over medium heat. Add the chile mixture and cook, stirring, for 5 minutes.
Add remaining 5 cups stock, carrots, potatoes, oregano, and salt. Bring to a simmer and cook until vegetables are tender, 15 to 20 minutes.
Add shrimp and simmer gently until pink and opaque throughout, about 3 to 5 minutes. Stir in lime juice and adjust salt.
Ladle into bowls and sprinkle with cilantro. Serve hot with lime wedges if desired.