How do you check the number of users?
You have to log into all 6 pools and see the statistics for the last block payout and see how many pages in 10s of users are there.

That's what I did when the 50mh/s limit per account was enforced and I saw on one pool the number of users jump gradually from 26-27 pages to 33-34 pages, meaning that we had on a single pool a 25% increase in users as soon as that limit was enforced.

So I guess if you take out statistics from the 6 pools which consist of current pool hashrate - current user count, then we might have some more info on this strange behavior.