Site crashed due to a possible memory allocation issue

The other day my site crashed, I followed this tutorial and when I opened the error log file I was greeted with this:

[Sun Sep 20 06:27:53.965600 2015] [mpm_prefork:notice] [pid 19095] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.9 configured -- r$

[Sun Sep 20 06:27:53.965651 2015] [core:notice] [pid 19095] AH00094: Command line: '/usr/sbin/apache2'

[crit] Memory allocation failed, aborting process.

[Sat Sep 26 01:54:31.107259 2015] [core:notice] [pid 19095] AH00051: child pid 30128 exit signal Aborted (6), possible coredump in /et$

[Sat Sep 26 02:32:21.725614 2015] [mpm_prefork:notice] [pid 19095] AH00169: caught SIGTERM, shutting down

[Sat Sep 26 02:32:22.507144 2015] [mpm_prefork:notice] [pid 30460] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.9 configured -- r$

[Sat Sep 26 02:32:22.507941 2015] [core:notice] [pid 30460] AH00094: Command line: '/usr/sbin/apache2'

[Sat Sep 26 02:49:02.616280 2015] [mpm_prefork:notice] [pid 30460] AH00169: caught SIGTERM, shutting down

[Sat Sep 26 02:49:18.401628 2015] [mpm_prefork:notice] [pid 1096] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.9 configured -- re$

[Sat Sep 26 02:49:18.404104 2015] [core:notice] [pid 1096] AH00094: Command line: '/usr/sbin/apache2'

[Sat Sep 26 02:49:40.540312 2015] [core:notice] [pid 1096] AH00051: child pid 1109 exit signal Segmentation fault (11), possible cored$

[Sat Sep 26 02:49:49.553012 2015] [mpm_prefork:notice] [pid 1096] AH00169: caught SIGTERM, shutting down

[Sat Sep 26 02:49:50.430461 2015] [mpm_prefork:notice] [pid 1392] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.9 configured -- re$

[Sat Sep 26 02:49:50.430623 2015] [core:notice] [pid 1392] AH00094: Command line: '/usr/sbin/apache2'

The first thing that jumped out at me was this line:

[crit] Memory allocation failed, aborting process.

So I ran the following command and got this result

:~# grep memory /var/log/dmesg
[    0.000000] Scanning 1 areas for low memory corruption
[    0.000000] Base memory trampoline at [ffff880000099000] 99000 size 24576
[    0.000000] init_memory_mapping: [mem 0x00000000-0x000fffff]
[    0.000000] init_memory_mapping: [mem 0x3ea00000-0x3ebfffff]
[    0.000000] init_memory_mapping: [mem 0x3c000000-0x3e9fffff]
[    0.000000] init_memory_mapping: [mem 0x00100000-0x3bffffff]
[    0.000000] init_memory_mapping: [mem 0x3ec00000-0x3fffdfff]
[    0.000000] Early memory node ranges
[    0.000000] PM: Registered nosave memory: [mem 0x0009f000-0x0009ffff]
[    0.000000] PM: Registered nosave memory: [mem 0x000a0000-0x000effff]
[    0.000000] PM: Registered nosave memory: [mem 0x000f0000-0x000fffff]
[    0.000000] please try 'cgroup_disable=memory' option if you don't want memory cgroups
[    0.012025] Initializing cgroup subsys memory
[    0.041090] Freeing SMP alternatives memory: 32K (ffffffff81e6c000 - ffffffff81e74000)
[    1.370191] Freeing initrd memory: 18780K (ffff88003ed99000 - ffff88003fff0000)
[    1.376662] Scanning for low memory corruption every 60 seconds
[    1.691925] Freeing unused kernel memory: 1332K (ffffffff81d1f000 - ffffffff81e6c000)
[    1.699187] Freeing unused kernel memory: 828K (ffff880001731000 - ffff880001800000)
[    1.704548] Freeing unused kernel memory: 700K (ffff880001b51000 - ffff880001c00000)
[    5.250658] [TTM] Zone  kernel: Available graphics memory: 508964 kiB

I have very little experience with deciphering error logs files and so I have two questions:

• Based upon the info in the error log file would it appear that my site crashed due to a memory allocation issue?

• I have no idea what any of the results mean after running the command

:~# grep memory /var/log/dmesg

Is there anything there that I should be concerned with?