Click into the recipe you want to modify either directly within plan view screen or within plan's schedule edit screen.
In the recipe details view click  "More Options...":

Then click "Edit":

From here, you can make changes to your recipes - including removing unhealthy ingredients and substituting them with healthier ones. The best part? You can watch our health rating change in real time as you type in your ingredients!

After you are done with your changes, click on "Save Changes".