Hi Christina,
It is late and I may not have read your post as thoroughly as necessary ... but here goes anyway.
My most immediate thought was that the "funky stuff" you refer to was either:
a) jpg preview artefacts, or
b) posterisation
Is that funky stuff visible around the edges of fine detail against the sky/water? (perhaps particularly when the image
is viewed at 100%)
Or is it on smooth tonal gradations of say, the blue sky? (perhaps particularly when the image
is not at 100%, i.e. it is being viewed as a 'full composition')
If the first - I suspect it might be noise - you mention the blue channel (the weakest) and worse at higher iso.
If the second - I suspect it might be caused by LR working in 8, not 16 bit mode when processing.
I don't know how LR does the switch, but it always puzzled me why ACR (Adobe Camera RAW) in Photoshop or Elements defaults to 8 bit mode and needs to be manually changed, via the hyperlink-cum-droplist in the lower edge, centre of the screen.
Can you do a few 100% screen grab/crops to show us the funk?
Cheers,