Please explain (for someone not so technically knowledgeable)
Sorry. Here's some technical junk. Read the following paragraph and if it makes no sense - don't worry, just keep reading.
One of the common adjustment tools for RAW files is a 'curves' adjustment. It's like a line running through a graph that represents the range of bright and dark pixels in your image. You can change the shape of the line (up is brighter, down is darker) and you can make curves to smoothly adjust certain pixels, of certain brightnesses, separately from others. For example, you can lower the brightness of the shadows, while raising the highlights. Anyway, if you bend the line too far, you pull the ends from the corners of the graph (where they start and are most natural for your image) and you start to loose details in portions of the image. When the curve has sharp bends, thing look bad.
Your first two example images look like they have had too much adjustment made to the highlights in the image. basically if white is the brightest (say 100%) and black the darkest (say 0%), it looks like your first two images got overly 'processed' in the brightest 25% of the range... Almost like your camera tried to brighten the pixel from 75% upward and then darken the pixels from 95% upward. If you brighten the 'prety bright' pixels more than the 'very bright' pixels - to the point where the brightest pixels look darker than the pixels that should be darker than them (pixels from 95%-100% are darker than pixels from 75%-95%) you get images that look a bit like yours.
Your third example looks messed up all over the histogram though (so I'm ignoring it) ;-)
Okay... I'll try to be clearer now
It's almost like your camera is over processing the RAW images when it converts to JPEG.
I haven't shot a single JPEG image in 10 years (other than on my very old cell phone). So take this with a grain of salt. But I do know the camera can be told how to process raw files. perhaps it's being told to process them in a way that is very extreme and somehow jives with your exposure settings. - That's kind of a guess... but it's an educated guess given that you've had this on two cameras.
If you have RAW files for these JPEGs, you NEED to look at the RAW files. If the RAW files are okay, you are somehow changing the internal RAW processing parameters. Theres a name for those, but I forget...
If your RAW files look like that, you live to close to a magnet factory, or area 51, or a black hole, or...