Leave shaders alone. And why do you run you mem so much higher than core? And up the -i untill the driver crashes and come back 1 level. The cards are playing chess with each-other at -i 13. Leave 13 on you card which is used for display and go up on the others. Your .bat should look like -i x,x,13 or 13,x,x depending which GPU u use for display. Spending 10 hours on the setting is not a lot. What happends if you run core=mem=1000?
I never use this pc, its made solely for mining also most people with 7970 at mining with much higher rates at -I 13....
The question is do you have/mined on a 7970?? because your post doesn't make any sense !!