I have a 2011 mac mini (the higher end model with graphic card). It has 16 GB of ram. I have created accounts for myself and my children. When I log into my account everything is working fine. However whenever my children sign into their accounts the mac mini becomes very slow and does not open any application. The mac mini is constantly being wirelessly backed up to a remote disc connected to Airport Extreme. My children also access some game sites. Kindly help us to resolve this problem.