Question about Bankroll fluctuation

A question to you regarding Bankroll fluctuation on multiple sites.
Over the last month my bankroll on one site has dropped by about %50 yet on the other site I play its increased by over %30(not too bothered as the rise is greater decrease in $ terms).
I play equally on both sites MTT's/Stt's/cash games etc.
Do you guys experience similar variance in your game and is this a normal occurance.