Bring 2 cups water to a boil in a saucepan. Add guajillo chile peppers and boil until soft, about 10 minutes. Drain and transfer to a blender. Add 1/2 cup fresh water and process sauce until liquefied. Strain sauce into a bowl.
Heat oil in a saucepan over medium heat. Add carrots, potato, onion, and garlic; cook and stir until slightly softened, about 5 minutes. Pour in the sauce and cook until combined, about 3 minutes more. Add remaining water and bring to a boil. Add bouillon and epazote. Simmer until vegetables are soft, 7 to 10 minutes. Stir in shrimp and cook until opaque, about 3 minutes more.