For 6 RX 570's you should be getting ~170MH/s. - I'm currently getting ~28.35 MH/s dual mining on the single RX 570 I have.
Long and short answer is, are you holding or selling? Selling right now, might be worth profit switching. However if you are holding, then... best guess is (and what I'm doing) is continue mining ETH - I'm using 8 RX 580's right now for it.
No man I am just getting 145 MH/s of hash rate. Each of the GPU is generating around the 24 MH/s and I have 6 GPU's in place. What I have acknowledged until now is that, they are not dropping a bit since I have fired them up and neither they are producing more than that. So everything stays the same for now.
My bets shot is to hold the ETH and hope for the prices to boost. Actually I am pretty sure on that, the prices might just boost up in month or so. If I get the chance then I will sell in that period just to get more closer to the ROI.