Very weird multi monitor problem (ultrawide works on windows, not on OS X)

Hi guys, So I'm running a hackintosh with the following specs:

-i7-3770K -Z77MX-QUO-AOS board -OS X 10.10.5 -EVGA 970 SSC

I purchased an LG 25UM67 for a second display, in addition to my main display, an LG 31MU97B (4K, connected via Displayport, no issues)

When I connect the new monitor, it only is able to run at 1080p (should be 2560x1080) and everything looks squished. However, under Windows (dual boot) the display runs at native res at 60 hz. SwitchResX seems unable to apply the specified settings when I give it a custom res.

Am I missing something here? I'm using an AmazonBasics HDMI cable, which is specified as conforming to HDMI 2.0. Please help!

Thanks!

submitted by /u/nerdpox
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