SQL Server doesn't use all available memory

Hi,

We noticed lately our web server has frequent SQL timeout from the application.
When we check the memory usage, the SQL Server is only using 1GB RAM instead of 7GB RAM we assigned in the option.

Before this, the SQL Server did use up all the available memory we allocated and we do not have this timeout issue.

Below is the screencap.

Is there any setting that may be changed or this behaviour is new from latest patch?

Thanks.

HSLaw