Were the 5 original tenants all signatories to the same lease? If yes, they are jointly & severally liable to all terms of the lease including ensuring full rent payment is made every month. When Tenant A skipped out, Tenants B-E were responsible for ensuring full rent payment continued to be paid. You did not have to find a replacement tenant.
Did the subsequent leases include Tenants B-E? If yes, each subsequent lease superceded the previous leases. You should consult with a local attorney for more guidance.