Most written lease agreements state somewhere that the responsibility for paying the rent is "joint and several." This means that each of the three tenants is responsible for the entire rent that is due during the term of the lease.
Is your Landlord letting the other two tenants out of their responsibility to pay the remainder of the rent?
Did you get permission from the Landlord to sublet or from the other two tenants? You should speak to the Landlord to get his permission first.