Are miners leaving?

Interval between blocks a few days ago was 10-15 min.

Here are timestamps of last 5 blocks
18131  Sep 22, 2015 at 3:35pm (UTC)
18132  Sep 22, 2015 at 4:35pm (UTC)
18133  Sep 22, 2015 at 5:10pm (UTC)
18134  Sep 22, 2015 at 4:28pm (UTC)
18135  Sep 22, 2015 at 5:59pm (UTC)

Was block 18133 mined before 18134 and 18132? Is that even possible?

Intervals between blocks (ignoring 18134) is now > 1 hour.

Last block was mined > 2 1/2 hours ago.

What's going on?