Delta 1637 today TUS-ATL. 45 minutes into the flight the pilot orders service discontinuation and for the flight attendants to be seated. OK, seems normal. 45 minutes later I asked one of the FAs what was up. He said there were "pressurization issues." We dropped from FL 34,000 down to 25,000 and continuing the flight as normal.

Anybody ever seen this before? BTW, not complaining, better than a divert.