Drop in expected earnings

Hi guys!

I have access to 2 rigs.

There is around 20% difference in MHS.

The earnings expected is around 45% difference.

What could cause that kind of difference?

The pool is the same, as the miner. Both of them are mining ETH. The hiveos version is the same too.

Expected earnings from now:

RIG1: 0.00904 eth
RIG2: 0.01445 eth

This is a new thing, been going on for few days. Before that the difference was as expected.