Final answer:
The question asks about specific ingredients in restaurant menu items, which cannot be answered accurately without the restaurant's menu information.
Step-by-step explanation:
The question pertains to specific menu items at a restaurant or food service, asking about the type of lettuce and onions used in a grilled chicken sandwich and a grilled mahi sandwich. Without information directly from the menu of a specific establishment, it would be impossible for me to provide an accurate response, as these details can vary greatly from one restaurant to another.