[SalesForce] Update custom object after insert trigger

You could resolve this by using a static Boolean variable in a class. Quoting from the success community

In order to avoid the situation of recursive call, make sure your trigger is getting executed only one time. To do so, you can create a class with a static boolean variable with default value true.

In the trigger, before executing your code keep a check that the variable is true or not.

Once you check make the variable false.

A detailed explanation with sample code is available on the link

The problem is with the scope of your variables. RecipeItemList is declared outside the for(Recipe_Sheet__c rec :trigger.new) loop so the items added to the list the first time round the loop and then inserted are still in the list the second time round the loop and so are inserted again which is an error because they already have an ID assigned.

Narrowing the scope of RecipeItemList so that it is declared and initialised within the loop will solve the immediate problem because each time round the loop a new empty list will be created as the starting point.

However, your code in both triggers does contain the anti-patterns of querying and doing DML inside a loop and so really also needs bulkifying.