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You appear to be using bounce flash, or possibly sometimes off camera flash, which is good, but I'm seeing the un-gelled-flash doing mortal combat with the tungsten ambient, which is alternately giving you varying degrees of strong orange casting on the background and sometimes the subjects, or a magenta tint, depending on how you've white-balanced.
If you gel your flash full CTO or 1/2 CTO, and white balance for that, you'll reduce the clash of light colors and make it harder to tell that the key light is (usually) coming from your equipment. Since you're bouncing, I'm pretty sure the flash you're using came with a set of gels likely including three orange ones (1/4, 1/2, and full).
I think Alan is correct: the problem isn't that you used HDR software, but that you weren't happy with your exposure and used a lot of Recovery in Lightroom. I think 24, 25, and 26 exhibit this problem -- the specular highlight on his forehead was probably nearly blown. In 26, your exposure levels (however you've set them in camera and in post processing) result in an almost grey-ish dress, especially near the bottom. You don't need to blow out the image, but a whiter-looking white dress is probably desirable.
I think you'll resolve some of these issues by gelling the flash and letting it work in concert with the ambient, rather than at odds with the ambient.