Well, I am at a loss of whats going on with my setup.
Got replacement card and the rig been mining about 12 hours.
Now I get notification of hashrate drop. I login to see a few of the cards at Zero.
Reboot Pi and only first 3 cards are hashing.
My room is at a constant 60F with fans blowing over the cards.

Set all chip speeds to something slow like 50 with autotune off, and restart chainmminer. If the problem persists, reseat the cards.