I'm running a Batch 3 Full and 1 standard for about 6 weeks now and haven't noticed any drop off. So a couple questions just to get some focus:

1) Is the reported hashrate from the Apollo web dashboard or your pool?
2) Are all 44 ASICS running on all 3 hashboards?
3) How do your hash board temps look? Mine have been right around 65°C since day 1 in Turbo mode.

The "designed" hashrate is an average and can vary by around 5% so dips down to 5.7ish Th/s on the dashboard should be expected.

Someone here will certainly have more information for you than I do.