Watcher logic help

[amStuckplsHelp]

Hi,

I have a few servers which supply the number of 'current active users' on those servers to my Elastic stack via Logstash.
I am trying to create a watch such that;
If the number of 'current active users' drops by 70% over a 5 minute period, then send an email alert.
So the basic logic looks like:
If currentActiveUsers(@time=now) < (0.3 * currentActiveUsers(@time=(now-5mins))), then send email alert.

Is this even possible?
The relevant parts of the Watch JSON looks like this but it definitely doesn't compile as is:

  "input": {
    "search": {
      "request": {
        "body": {
          "size": 0,
          "query": {
            "bool": {
              "filter": {
                "range": {
                  "@timestamp": {
                    "gte": "{{ctx.trigger.scheduled_time}}||-5m",
                    "lte": "{{ctx.trigger.scheduled_time}}",
                    "format": "strict_date_optional_time||epoch_millis"
                  }
                }
              }
            }
          },
          "aggs": {
            "bucketAgg": {
              "terms": {
                "field": "hostname.keyword",
                "size": "10",
                "order": {
                  "metricAgg": "desc"
                }
              },
              "aggs": {
                "metricAgg": {
                  "max": {
                    "field": "CurrentActiveSessions"
                  }
                }
              }
            }
          }
        },
        "indices": [
          "<useful_index>"
        ]
      }
    }
  }
"condition": {
    "script": {
      "source": "ArrayList arr = ctx.payload.aggregations.bucketAgg.buckets; for (int i = 0; i < arr.length; i++) { if (arr[i]['metricAgg'].value{{ctx.trigger.scheduled_time}} < params.threshold * arr[i]['metricAgg'].value{{ctx.trigger.scheduled_time}}||-5m) { return true; } } return false;",
      "params": {
        "threshold": 0.3
      }
    }
  }
 "actions": {
    "email_1": {
      "email": {
        "profile": "standard",
        "to": [
          "amStuck@sendHelpPls.com"
        ],
        "subject": "Active Sessions Alert!",
        "body": {
          "text": "Active Sessions Alert!\nThe number of active sessions connected to {{ctx.payload.hostname.keyword}} has dropped 70% in the last 5 minutes."
        }
      }
    }
  }

The syntax in the condition statement is very wrong but I am not sure how to fix it
Any help is most appreciated,
Thank You!