My recommendations:

1. Change the default value for max memory in SQL Server.

2. Leave appropriate memory for the OS too.

3. Check if there is memory presssure for SQL Server (If Yes, Increase the memory but also remember point 2).

4. If possible move the application to a different server (may increase the performance of the application).

5. If there's no memory pressure on the database and by limiting the max memory settings performance is not affected then you may leave the settings to that 😉 , Senior members please advise.