1.6.8 hashrates is lower for me

cards (both sapphire nitro+ 4gb) / hashrate 1.6.7 / hashrate 1.6.8
rx470 / 740 / 720
rx570 / 760 / 740
algo: bittubev2
i switch back to 1.6.7
You need set gpu by hand, not use auto. Auto value lower in 1.6.8
Intensity is 29 in auto mode (both cards). I tried 30, but the miner crashed. I tried 28, the hasrates was lower. I tried 29, the results was same. Which settings set up manually?