I don't think it is. I think it has to do with the Avengers season being over. Young Justice was slow to start, but it is about as good as the Avengers now, IMHO.
There have been 19 Avengers episodes aired not counting the additional 5 compilation episodes of the micro series and that thread was pretty dead the whole time despite several of us trying to bump it so more people would pay attention to it. I don't think the season is over since they would have advertised a season finale. I think they are on a break doing replays like all other shows during their season now though.
But back on topic, I like Young Justice but I don't find myself rushing to watch the episodes.