If Apache / HTTPS is using lots of memory on your server, here is how you can optimize Apache on your server / VPS.
Login as root in WHM and navigate to:
WHM Home >> Service Configuration >> Apache Configuration >> Global Configuration
And change value of Max Connections Per Child. Default value of Max Connections Per Child is 10,000
You should reduce this value to 1000. This will greatly reduce memory usage by Apache on your server.