I'm successfully dual mining ETC + SC but one of my GPU has lower hashrate than others. Never did dual mining before I have set dcri to 14 and I think it's optimal for the rest GPUs.

All GPUs have same Elpida's memory, they're same manufacturer and same modded bios. Have you any idea what's happen to that GPU 4?

Screenshots:
http://i.imgur.com/OnTrQZ9.png

after a while
http://i.imgur.com/oHhxv8W.png

When I solo mine ETC hashrates seems to be ok, no drop on GPU 4.