IF statement vs logical operator not working as expected

Hi I am wiritng a simple function to check on three different files existance in which it should return "yes" if ALL three files exist and "Partially" if one or more file exists and "no" if none of the three exist.

The functions is called IsPortalDown and it has a case switch; NodeOne is the one in use at this point.

Here's my function

function IsPortalDown() {
  case "$1" in
    NodeOne )
    if [[ -f $wpsdmgr ]] && [[ -f $wpsnodeagent ]] && [[ ! -f $wpsserver ]];
    then
      echo "Yes"
    elif [[ ! -f $wpsdmgr ]] || [[ ! -f $wpsnodeagent ]] || [[ ! -f $wpsserver ]];
    then
      echo "Partially"
    else
      echo "No"
    fi;
      ;;
    NodeTwo )
      ;;
  esac
}

A few constants are defined to clean things up a little bit. See below

PortalProfileLogsDir=/opt/IBM/WebSphere/wp_profile/logs
WPSDMGRProfileLogsDir=/opt/IBM/WebSphere/AppServer/profiles/dmgr01/logs
wpsdmgr=$WPSDMGRProfileLogsDir/dmgr/dmgr.pid
wpsnodeagent=$PortalProfileLogsDir/nodeagent/nodeagent.pid
wpsserver=$PortalProfileLogsDir/WebSphere_Portal/WebSphere_Portal.pid

Here's how I call the funtion and expected result below.

IsPortalDown NodeOne

If all three files exist the output shall be as below

[wpssrvr@tstdydalbpt0101 dmgr]$ IsPortalDown NodeOne 
Yes

If one of the three files exist the output shall be as below

[wpssrvr@tstdydalbpt0101 dmgr]$ IsPortalDown NodeOne 
Partially

If none of the three files exist the output shall be as below

[wpssrvr@tstdydalbpt0101 dmgr]$ IsPortalDown NodeOne 
No

My issue now is that if one of the three files or all three files do not exist I am constantly getting Yes instead of Partially.

Any help is appreciated. Thanks