Longer answer: "total reward" is sum of unconfirmed blocks and confirmed blocks. But *during* the block confirmation process the block is in transitive state, it's neither unconfirmed or confirmed for some time. So you'll see minor drop in "total reward" for small amount of time.
Of course, when pool is processing 30+ rounds in batch, you see such small drops more often. Especially when you're killing the webserver by F5 every few seconds

.
@ Slush
If you needed anything for the pool, but it was too expensive, what would those items/services/<insert here>...what would it be?
If you think things could be better than they currently are, what would you change about the way the pool operates or functions?