What is a good upper ab workout that can target only 1 side? *my left side is weaker than the right*?

my uppermost ‘Rectus abdominis’ on the right side just below the rib cage is stronger than the left, it may be from inconsitent ab workouts and from shooting (in water polo); i hope it isn’t a hernia. when i flex my abdominal muscles, it bulges out more than the other muscles. It seems larger than my other upper-ab muscles.