Closing 1st 4PLEX: Updating terms on existing Rental Contracts?

[Vibhu Arya]

Hello, I'm looking to close on my 1st 4PLEX in AZ pretty soon and there are existing rental contracts going in for next 6-9 months. The clauses of these contracts are super week and was wondering if there is a way I can update the clauses without breaking the lease term or change in rents $ now itself? 

I understand that once the rental lease terms are over then we can for sure change /update - BUT I see it as a risk now because of some missing critical clauses which have not been included in the original rental agreements by the seller.

Thank you!