We've been upgrading our infrastructure this weekend. Everything went according to the plan except our crawlers are very slow right now. The are the plenty of the pages that has not been checked for as long as three days.
We are doing our best to isolate and fix the problem, but the is no ETA right now. We hope everything will be back to normal in a couple days. We will keep you updated.
Update (March 16): Our crawlers hum with even greater speed then before. We expect to clear all backlog in a couple hours and things will be back to normal again.