I had the same issue and didn't notice it had defaulted to 8 bit, why on earth would PP software NOT use 16 bit, instead of reducing the quality and number of colours in an image?
I processed lots of images without realising the change when I started using the new laptop, and was so disappointed at the colours and especially skin tones. I was blaming the laptop/colour profiles/screen/printer, but as soon as I changed back to 16 bit, quality returned.
Gramps has the solution, good luck.