The owner may not listen to your request in this regard, he will insist on deducting the rent which the Nestaway had not paid to him.
You can ask the owner to deduct the same but ask him to give it in writing tht since the Nestaway group had not paid the rent for the month of August, they are deducting the same from you.
After that you can demand the return of the rent from Nestaway on the basis of the written receipt by the owner.
Since you are not knowing the facts, you may have to believe the words of the landlord.