How can I make empty the physical memory from my hosting server ?

Hello,
I host 9 domains on my hosting server and now all sites getting down because physical memory is almost full.
please check this screenshot : http://prntscr.com/3j9bqx

due to these I can't access my sites, Please gimme suggestions to re-live my sites gaian.
All of my sites getting good search traffic from google and I think if I did not solve this issue so I may loose my positions from google .

Please help !!!!

Thanks

aah just getting reply of my ticket from supports

hi, we performed the kernel upgrade, it was a downtime for a few minutes, the sites are back

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It looks like your web hosting provider is using Cloudlinux for their shared hosting clients. Cloudlinux allots a certain amount of server resources per cPanel account (I/O, concurrent connections, and memory).

If you find yourself running out of resources I would suggest getting a second cPanel account from your provider as this will give you more resources.