Put simply, my AE2stuff crystal growth accelerators disappeared between when I logged off and logged back in again a few days later.
This seems to be a known, open issue on the AE2stuff github, issues 168, 176 and 178 all seem to describe my problem. The issue seems to be old, so a mod update seems unlikely to fix this for now.
These issues list two main solutions: connecting them with quartz fibres, and moving the security terminal. I've added in quartz fibre connections, and shifted my security terminal onto a different colour cable line to the accelerators. I'll post an update here once I know whether this has worked
EDIT: Update on progress: Quartz fibres appear to have fixed the issue for growth accelerators. However, simply having Advanced Inscribers on a different colour cable still disappeared, so Quartz Fibre connections appears to be the more reliable fix.