You can run the amps with no 6AQ5s but with the 12AU7 and the 6080. This will cause the OA voltages on the high current boards to rise and Kreg voltages on the center board to be 0, but everything else can be evaluated under these conditions. This is where I would start.
If a B side heatsink is getting warm, it may help to post some build photos and we may be able to spot a miswire.