Theres different ways to change a recipe, and it will have different effects based on where you are doing the changes:
Recipe in client meal plan directly: This will be a local change on this specific client's meal plan. No changes in general for other plans.
Recipe in libraries (or opened through a meal plan template): Here's the main recipe itself. Changing this will have an effect on all existing templates but not on plans already created for clients. (The reason for this is that plans are aopied to clients; they are not 'subscribing' to a meal plan).
So if you are changing something on a recipe in libraries and want this to be changed on existing client plans as well. You will have to manually open a client plan, remove the recipe, and read the same recipe again. (Or just remove the whole plan and re-add the plan one more time) 😊