leak at quick connector

Any suggestions on fixing a leak at a quick connector?  Attached photos show the connector up close and the bigger picture.  The up close shows the connector and another fitting on the right.  I am not sure what the purpose of the smaller fitting on the right is - seems like the tubing coming in from the right should just go directly into the quick connector - something I am not understanding.  I think the leak is at the junction between the two fittings.