However, i ran a VRAM check and realize both have different MiBs 12206 MIB and 11441 MiBs.
Can anyone explain to me why is there a difference in both of these K80s?
Just a guess: Do you have ECC enabled on one GPU and disabled on the other GPU?
Use nvidia-smi to display (and change) the ECC status. ECC status is persistent. With ECC enabled, a certain amount of memory (I seem to recall 6.25%) of the total physical memory will be used to store the additional bits used for error correction, reducing the amount of memory available to CUDA applications.