30 websites stopped working due to Appliaction Pool issue by Plesk?

[MahendraC]

I am hosting reseller from India. Few days back my 30 websites stopped working suddenly. When asked to my ISP who provides me Plesk Control Panel to manage my resellership, my ISP said the sites were stopped by Plesk due to Application pool problem in one or more domains. My Reseller plan is on shared server with this ISP. The sites started working after long time when they said they did reset/recycled application pool of all the sites. They also asked me to enabled application pool setting for all domains, which I did for almost all domains.

I want to know is this possible that all of my sites can be stopped by plesk, if any one domain creates problem due to traffic? Either yes or no, how can I avoid this problem?

What more information you may need to know this issue? Thanks in advance