By August 1943 they sent a postcard from Theresienstadt, to which they were deported.
According to Yad Vashem records, they both died there by 1944

Postcards from Rosa and Ascher Mayer    Postcards from Rosa and Ascher Mayer

Th. 1.8.1943

My dears,

We have arrived in good health, hopefully you are also feeling well. Please write us often, even though we write rarely. Small packages, letters and parcels reach us punctually and we are very happy about them. We think of you a lot and greet you heartily,

your Ascher Mayer
and Rosa Mayer