While on the phone, but still watching the MEDM screens of SUS's in BSC8, I saw the values coming in off the front end freeze. After some investigation, I found that the IOPs for both front ends that control H2SUSITMY and H2SUSFMY had lost their IRIG-B timing -- H2:FEC-28_IRIGB_TIME, H2:FEC-28_IRIGB_TIME were some large red number (normally green and around ~15 us). This also seems to have caused all the running models on those front ends to have a red 0x4000 status with regards to the framebuilder / daqd.

I'm not sure why all this happened, but I've restarted the processes on both front ends and all seems fine...