This is a GE F32T8 about 4-8 years old? 

Indeed... Did it lose vacuum when it burned out? If it loss vacuum, it could have blown in the phosphors by the in rushing air.

I've seen similar results with GE F32T8 lamps of that vintage at my place of work. Wasn't there for the show, though. Sometimes the phosphor is yellowed. That looks to be blown phosphor when the air rushed in.

This was at my work.  fixtures above the desks.  Did not get to see it either, I was taking out bulbs above my desk as I get headaches from overhead fluorescent lamps after sitting for more than 30 minutes with having to look at my computer monitor all the time.  These fixtures are on sometimes 24 hours a day and will get turned off maybe once or twice a week for 8-16 hours if lucky.  Been that way since the building was built around 1999 or so.  I can't see any cracks in the tube but will give it a closer look, probably the end cap let loose or something. 

Sometimes the crack is at the junction of the lamp with the end cap. Hard to see, but enough to let in air.

Or at the stem, which is entirely under the cap - in this case you might be able to see it only through the lamp where the phosphor is blown away

Sometimes the crack is at the junction of the lamp with the end cap. Hard to see, but enough to let in air.

I would rather expect the crack to be around the lead in wires - as they significantly heat up at lamp EOL...