but also: have you set the microadjustment settings for this lens? you definitely have to do that if you intend to shoot f/1.4...
are there any tutorials explaining how to set the Microadjustment on the camera? I know where the settings reside on the camera menu just need to know when to adjust for a lens.
Even if you had the perfectly calibrated lens with your camera, f/1.4 is far too shallow depth of field for a photo like this, it wouldn't even matter. They'd still look mostly out of focus. You need to learn the "proper" technique, or learn to line your subjects up perfectly and stop down only slightly. Or just learn to stop down enough for every photo situation. As much as I love f/1.2, or f/1.4, you don't need to shoot everything that way. That's the wrong approach. Choose your background, light, lens and camera settings properly, and you'll always get better photo.