Rent issues in student rental agreement?

Hi, hopefully Property118 readers can provide some advice.

My daughter is a tenant (of 4) in a student rental where one of the students has not paid any of their rent (now 7 months into a 12 month agreement). The tenant in question told the other flatmates and the agent that she had paid in advance (she signed the 12 month tenancy agreement as did the other flatmates).

The tenant never moved in even though she said she would be moving in a number of times. The tenant never paid anything in advance. The agent only notified the other tenants 6 months after the tenancy started that this tenant had not paid – we believe that the other tenants were not notified until 6 months due to 2 of the tenants paying the full year in advance, which the agent used to cover that fact that one tenant had not paid their rent.

The agent has basically said they have tried to get the tenant to pay but can’t and therefore the other tenants are liable as they are joint and severally liable. The agent has said that they “missed” the fact that the tenant had not paid in advance at the start of the lease because of the large payments (ie. the advance payments of the other tenants). The agent’s approach is there is effectively one tenant. The agent has not notified the landlord.

What are the obligations of the agent to notify the other tenants if one tenant has not, or is not, paying the rent? The agent was chasing the tenant for payment so they knew she had not paid.

Is the agent allowed to use rent in advance from one or more tenants to cover the rent not paid by one of the other tenants? The agent has said they can do this.

Where is the enforcement of the signature on the tenancy agreement made?

Thanks in advance for any advice,

A