Why does my hashrate drop suddenly?

I've noticed this issue occurring when I'm messing with MSI AB and I apply some settings, or it will happen by itself sometimes. My initial hashrate with 3 r9 390's is around 88.5Mh/s and drops to ~30. The first two gpu's lose hash rate while the third gpu stays in full hash rate.

I have also seen the opposite happen where the first 2 gpu's hash rate lowers and the third gpu increased its hash rate by 5 times.

Windows 10 64bit
3 R9 390
H97 Anniversary
1000W PS