Hm. That is odd.
I don't have the same problem as you (in fact my lease rates were about completely flat for well over a year), but Between Week 4 and Week 5, my lease expenses went up about 15%. But no leases expired at that time to be renewed, and even if they had, my expenses wouldn't have climbed that much in a single week. And I haven't leased any aircraft in years, so it's not new leases either.