Getting some underperformance with OC settings

Hi all,

So I moved my 3 AMD cards into a rig and the cards are not doing as well as they were individually in their own machines. I am following the settings in the link below for the two 570s, and I have one 470 in as well without any OC, doing just as well as the two 570s that are OC'd. They were getting about 12-13 MH/s individually, but altogether in the rig they are pulling only 9-10 each. They all have compute mode on. I still consider myself new to mining, so, forgive my ignorance if the answer is obvious.

https://imgur.com/a/ePa4Mlb

I also just tried setting the cards to automatic overclock in the Radeon settings app, and that brought their hashrates back up to 11-13 each.

Can anyone advise me?