Actually the opposite, My Musical was S6E6, which if you count the dots is one of the highest rated of the season. Looks like the low in season 6 was the Night to Remember, which was literally a clip show of the previous six seasons, which tend to be panned by viewers since it's just rehashing older episodes.

Edit: Other fun fact, the other high point of the season seems to be my long goodbye, where a supporting character goes into a coma and ultimately dies.