If you're comfortable with Javascript, pick up Yanfly's Script Call Plugin Commands plugin. This will let you build your update with custom text added to the quest description. So, I'm going to make an example here that your quest is #30, and the added text is, " Too bad the party came up empty, now they have to investigate elsewhere."
First, you'll have to use the script commands, since you'll have to build your statement for the Script Call Plugin.
Code:
var CurrentDescription = $gameSystem.getQuestDescriptionIndex(30);
var UpdateDesc = '<br>Too bad the party came up empty, now they have to investigate elsewhere.';
var NewDesc = CurrentDescription + UpdateDesc;
var update = 'Quest 30 Change Description Entry To \"' + NewDesc + '\"';
CallPluginCommand(update);
I'm sure there is a way to build a common event around this, but it's too early for my head to be on straight. Also, I may not have it exactly right (I just woke up). The JS for getting the quest journal description is already in that plugin, so you just add the text to it and use the Script Call Plugin to make it happen.
If you need to be able to do this for a few quests, this should be fine. If you have a large number of quests, it would get unmanageable really quickly.
edit: I forgot to escape the quotes for this. Fixed.
edit 2: Keep in mind that this is a quick and dirty answer, so, please, take it with a grain of salt. I've not used the quest journal lately and am rusty with the commands