Can someone help me understand why my concrete5 site might have a server error? It went down last night when I was asleep, so can't figure out what might have changed. My host sees no issues, all my other sites work, including a very similar Concrete5 site. My host says it may be plugin related, but not sure how to verify that. I have not added new plugins recently.

I tried looking for weird things in htaccess and went to older version with no luck. Tried increasing memory_limit, no luck. It has been down for like 7 hours now.

Thanks for any suggestions you can give.

Site:http://gospelriver.com

Update:php error log says PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/apc.so' - /usr/lib64/php/modules/apc.so: cannot open shared object file: No such file or directory in Unknown on line 0

Also getting this error:
PHP Fatal error: Uncaught exception 'Zend_Cache_Exception' with message 'The apc extension must be loaded for using this backend !' in .../updates/concrete5.5.1/concrete/libraries/3rdparty/Zend/Cache.php:209

I contacted my host about possible apc issues but haven't heard back.

Could there be a bug in caching? gospelriver.com uses some caching and aguadelavida.info does not.