It is stable since few hours. Here is the screenshot.
https://prntscr.com/imnsah
What is tune-up settings?
https://prntscr.com/imnsah
What is tune-up settings?
I mean your Over Clock setting and it's has been shown in your screenshot.
4 GB Polaris cards stable on 28,xx MHs it's good enough. Stable more important than raising your Hashrate.
6 cards and system take 820W from the wall.