You are choosing too low a value in quality at your save as jpeg step.
It is called posterization and is very common, it has nothing to do with camera settings or your other processing. Do it again but save the jpeg at over 80% quality, sometimes you even need to use 100%.
Private... are reducing file size and lowering IQ the only reasons why someone might choose to save at less than 100%?
Just wondering if I'm missing something...
For the vast majority of images, nearly all of them, anything more than 80% is just a waste of space. I have my "Save For Web" defaulted to 80% because it is very rare for images to need more and the size over 80% expands very fast, but will often use it much lower. Effectively you gain nothing for much more space.
Why does this matter? Well it isn't just for HDD space, many images are emailed, where even big companies put relatively small attachment limits on messages; uploading to websites like CR, don't forget not everybody has good download speeds so image optimisation is a very important factor then so others can see your images; also uploading to online print services, most people have much slower ADSL connections rather than SDSL, uploading takes much longer than downloading, those files to print can take forever to get sent to the printers and slow everything else down in the process.
If you have a workflow that involves you saving as jpeg then absolutely save at 100%, but there are few (none!) reasons I can think of where that is the most efficient option, for everything else jpeg compression, assuming you have finished your post processing, works very well and speeds up anything and everything you then do with that jpeg.
Jpeg is a lossy format, it is designed for you to take advantage of that and throw away everything you don't need to display the finished image accurately, it is not an archiving, storage or intermediate format where further work or more advanced processing from newer processes is used. Just look at Lightroom Process Versions over the years, 2003-2010-2012 dramatic differences in processing capabilities to lossless images, totally lost on jpegs.