So I was under the impression that the difficulty just meant that blocks were found more slowly.  But it appears that my hashrate has fallen about 20% across all of my miners.  Is this to be expected?  I'll check the miners when I get home, but I thought my MH/s would remain unaffected, I would just have a smaller payout.

I guess I'm still a little unclear how the difficulty affects the mining.  Can someone enlighten me on what my expectations should be?