Game runs smooth on first monitor and video preview in OBS is choppy in second monitor.

[Alex Dorades]

When i play a game in first monitor the game plays smooth, no problem. As soon as i alt tab to the desktop and then return to the game again, in second monitor open broadcast software shows me in the preview of the video choppy/laggy. I noticed that, when i alt tab the game, i play, obs shows me the game playing well but as soon as i return to the game obs shows the video preview choppy.laggy again. Why is this happening. I thought maybe my system cant afford that but thats not happening with that PC.

I74790K
980TI
MSI MPOWER MAX AC

 

[Alex Dorades]

Its like when i play a game the second monitor becomes inactive.