If you schedule a recipe into a Meal Plan and then edit the recipe, the changes are not automatically reflected in the Meal Plan.
You can choose to update a recipe within any Meal Plan in which it is used.
Under 'Cookbook' (1), click into the recipe you want to update and click 'More Options...' (2)
Then click 'Update Copies in Meal Plans' (3)
Check off (4) any of your Meal Plans in which this recipe is used that you want the updated version to exist. Click 'Update' (5)