Quick question about agents & credit referencing

I have had the same tenant for about three years now. The original tenancy was for a couple but about a year ago they split up and gave notice to leave.

I had lined up some new tenants, through my agent, but then one half of the couple decided they wanted to stay alone. A new tenancy agreement was signed but as her financial situation had changed (i.e. one income, not two) should I have expected the agent to do new credit check?

Thanks...