Thanks for the suggestions masmullin. I have tried mining with just 1 miner plugged into the hub and the pi with still lock up. There doesn't seem to be a correlation with how long it takes to crash and how many miners are being used.
Looking over at this post https://bitcointalk.org/index.php?topic=253749.0
Plugging 7 miners in the DLink hub is too many. It sounds like most people are successful with only 6. Since I am only running with 5 I don't think I am running into any power issues.
When I say the Pi locks up I mean it REALLY locks up. No keyboard input works and I cannot even ping the pi. So I don't think setting up a watchdog process would help.
Using jdb's suggestion and adding slub_debug=FP
to /boot/cmdline.txt has pretty much solved the issue. I have been mining non-stop for 3 days now with no issues. I think this means it's most likely a software bug.