Goals from Heidar Helguson and Joe Mason put Cardiff ahead before Charlton struck back with five goals of their own to leave the Welsh side stunned.
Craig Noone and Aron Gunnarrson struck late on to put the home side under pressure but Charlton held on to secure a victory that, combined with other results, saw Cardiff drop to third in the Championship.
"You can't legislate for individual errors," said Mackay. "We started really well and played as good as we have played away from home this season.
"Then David Marshall drops one he would normally gather and Johnnie Jackson will never score an easier header.
"And if Marshall loses a goal from 50 yards again I will be amazed, he had been fantastic this season.
"We lost our shape after that and players who have been consistent all season started doing things they wouldn't normally do.
"But I have a group of payers that have been incredibly consistent this season and we need to make sure we go out there on Saturday and stop the individual errors - four goals could have been avoided tonight because of that.
"Teams go through runs in this league and we are on that at the moment."