its likely a coincidence, usually when you get extra CTAs in the web interface it means the board has failed and reset, when it reconnects to cgminer it is added as a new device, i think i have a rough idea of whats likely happened but its only a somewhat educated guess. when it was running at 1.2 chances are one core on one of the boards was overheating and being throttled or even temporarily disabled resulting in the lowered hash rate, however after it hits a certain temp (i believe around 120C) the board shuts down completely, it then restarts and gets re-added then fails again.

if you open up the rig and connect the board to cgminer with cointerra enabled youll get better error reporting, by no means is it concise but it will at least tell you when the board resets or gets disabled, sadly ive never gotten a board back to full power but i have got some from dead to running at half power. if you happen to be lucky then it may be as easy as replacing the thermal compound on the problem board, but sadly ive found its rarely that easy