Submission guidelines for the case of second ITA

I couldn’t submit the documents in time when i received my ITA last time.
I got an ITA during the latest round of draws.
Is there any explanation i need to provide while submitting the documents for the new ITA.
Also, my medical examination is done before i received the second ITA. Does it still hold good?

Your medical exam is valid for one year so it’s probably still good. Although, your PR visa, once you get it is only valid till the medical exam is valid so keep that in mind.
Usually 3 months are sufficient in most cases to get all documents. The only documents that take time are ECAs, and reference letters depending on how quick your contacts are to respond to you (FBI used to take time but now I heard it’s all online and quick).
My guess is that you may submit a letter of explanation to say why you are not able to submit the documents in time but it’s all down to the case officer if they will accept your application or cancel it and ask you to reapply. Usually CIC tends to me lenient but you never know.