Copying an NSArray with mutable copies of the original elements

I am creating an array of dictionaries in a class. I want to return a copy of that array to any other object that asks for it. This copy that is passed to other objects needs to be modified without modifying the original.

So I am using the following in a getter method of my class that holds the "master" array:

[[NSMutableArray alloc] initWithArray:masterArray copyItems:YES];

However, this seems to make all the dictionaries inside immutable. How can I avoid this?

I think I am missing something here. Any help will be much appreciated!