i have 2 computers with the same cards (some parts are different) but they have the same hash rates using same config and sdk (different amd cata).
you can check the wallet address on my screenshot to check my info reflected on the site. (while i am writing this, my correct hash power is displayed on the site and "blank" rejected hash rate. as for the fan, i need to use 80% to 100% because i'm in a tropical country.
And that brand this 280x are ? I bet not all can handle a mem speed 1800

funny that the cards that i bought were locked on specific value at first (E:1070 M:1500). I forgot what i did to unlock them. I think i just entered the values while i am creating the .bat file and also i attempted to change it on cgminer while it is running.
** when i tried to change it on the cmd of cgminer, it always says failed. what i did is while cgminer is running, i went to cgwatcher >> manage profiles >> look for the .bat file then right click "edit" then save >> then restart miner and it worked.