Has anyone elese noticed the estimated reward for the current round is dropping like your mining has stopped? Estimated reward is now down to 0.00004556 BTC

Normally I get 0.00030000 BTC or somewhere in that region. the last 2 or 3 rounds show a slightly lower reward than normal but I neglected that as natural fluctuation but only just noticed my estimated reward for this round is dropping by the minute the same as it does when I stop mining, yet all my workers still show last hsare as 0 minutes ago and I can't find any problems with their speed etc

Edit - It seems to be going back up now, anyone know why this might have happened?