when i mine only ETC i get 26mh/s single rx 470
if dual mine etc+dcr only 20 for ETC and 600 in DCR
is that normal
Yes, it is totaly normal with dual mining on AMG GPUs.
Only nVidia GPUs have the same hashrate with simple and dual mining.
This is not true.
Try to fiddle with -dcri option.
I am mining 28Mh/s ETH and 750Mh/s DCR on RX 570.
But RX 5xx are probably better on dual mining.