I have a server with these specification:

*CPU*
Intel(R) Xeon(R) CPU D-1520 @ 2.20GHz
Cores : 8
Cache : 6144KB
*RAM*
2x 16384MB
*Hard Disk*
2 x 300 GB
2 x 2000 GB
*Software*
Ubuntu 14.04
Linux 3.14
Apache2 2.4.18
PHP 5.6.33
MariaDB 10.0.31

With one WordPress site and suddenly for the past two days Apache server used full RAM. I'm using cloudflare, I disabled wp-cron, increase memory size up to 60 GB. And the problem is still exist, any help what should i do?