I have a Tor exit relay for about 6 months and assign 1600 KBps for 'RelayBandwidthRate'. Until a week ago, used bandwidth on my relay was equal to 600-700 KBps. But in this last 6 days, used bandwidth reduced to 10 KBps. I did not change the configuration files and now I don't understand reason of this.

What events may have occurred? What is the reason?