Hi:
Any idea why one of my rigs is mining EXP (not dual)?, exact same cards as in the other one which is mining KRB... I would like both of them mining EXP (or ETH or MUSIC or whatever) + DCR, I accept one mining KRB but why only EXP?.
How it works?. I'm losing $0.50/day versus KBR, and more vs dual mining.

There could be a couple of reasons for such a situation - hardware differences (e.g. even GPUs of the same model probably differ on their ASIC quality), OS and drivers differences (no two installations are the same) computer state during the benchmarking could be different, and more.. its really hard to say without thoroughly examining the case.
If you would like to overwrite the WinMiner optimization logic you can simply force WinMiner to mine the coins you want it to - so in your case you can simply choose only KRB if you so wish, though this is not recommended as coins attractiveness and availability for mining changes rapidly (e.g. SIGT block size halved and will soon cease being POW, DMD in 10 days will cease to be POW, etc..)