Facts
A. On 27 December 1993, C.X. and B.X. leased a 3.5-room apartment of 79 m2 in Morges. The net monthly rent was 1,155 CHF, plus an advance payment of 70 CHF for heating and hot water. On 29 November 2002, the lessor agreed to reduce the rent to 1,000 CHF, plus the 70 CHF charge advance, effective 1 April 2003. On 20 December 2012, the tenants submitted a new request for a rent reduction to 870.03 CHF, effective 1 April 2013, citing the decrease in the mortgage interest rate from 3.75% to 2.25% and the increase in the CPI. The lessor did not respond. On 7 February 2013, the tenants filed a claim with the Conciliation Commission for Tenancy Matters, and then filed their request for a rent reduction with the Vaud Rental Tribunal on 11 April 2013, concluding that their monthly rent should be set at 871.50 CHF, plus charges, as of 1 April 2013.Considerations
2.1 When a tenant requests a rent reduction due to a decrease in the reference mortgage interest rate, the judge applies the relative method. This method involves examining, based on the calculation bases of the last rent determination, how these bases have evolved and whether they justify an adjustment of the rent. A change of 1/4% in…