JSON arrays with square brackets problem

I have a problem when sending JSON data to Elastic from Nifi - Nifi puts [ square brackets ] around a JSON array, and so Elastic doesn't recognise the data. The current fix is to use a SplitJSON processor, which removes the square brackets, but this will become unworkable when the number of flow files gets a bit big in number. Is there a way of creating an array of JSON that is recognised by Elastic that does not contain square brackets?

I am also using an older version of Nifi - Ver 1.12.1