Should I be concerned?

FreePBX 2.5:

Your memory_limit, 64M, is set too low and has been increased to 100M. You may want to change this in you php.ini config file
Added 0 minutes ago

well you may want to consider taking the advice of the warning message, that is why it is telling you that:-) It tries to increase the memory limit in the application but there may be some distros or environments that do not allow that so better to increase it in your ini file directly.

Changed it at /etc/php.ini Do I have to restart any services for this to apply?

probably: service httpd restart

Message went away
What did it mean though? Needed more RAM for some applications?
What usually causes this to happen? This box has been running for 3 years straight and this message came up out of nowhere after installing freepbx 2.5

because there were a lot of people who very often ran into problems particularly when doing module_admin updates with lots of modules and it would just fail. This was one of the reasons and we never checked and reported that.

Since we don’t believe in making money in our support services by fixing dumb things like this for people over and over, we instead chose to try and dynamically fix it as well as warn the users. It was not introduced until 2.5.

Oh I see.
Thank you very much