Like almost every other show on Good Friday night, Starz' Spartacus: Blood and Sand saw a drop versus the previous week. It still managed to have the second-best viewing average of the season for the initial 10pm airing, trailing only last week. Still a significant drop with adults 18-49, though, at least against the previous week's season high.
There's two episodes left in season one, I'm guessing it will rebound next week and end the season with season high numbers.
If you're a Netflix subscriber you can catch up on season one of Spartacus: Blood and Sand online. If you're not a subscriber you can get a free one month trial and watch season one for free.