Yes. As all tenants sign one tenancy agreement, each guarantor will be liable for the total rent. The tenancy is a joint and severally Assured Shorthold Agreement. What it means is that all of the tenants on the agreement are joint and severally liable for the whole property, and all of the rent. This means it is not possible to guarantee a specified share of the rent for an individual on that agreement, as they are responsible together for all of the rent. This is a standard type of agreement, and used by most agents and landlords.
If you do not want to stand guarantor for the entire group, the tenant can pay the rent in advance or take out an insurance through a company such as https://www.housinghand.co.uk/