I perfectly understand what you’re saying, but the tiff was merely a good way for him to render an image out to me in high enough quality so that I wouldn’t lose even more quality, i.e. re-rendering out to a jpg would lose even more quality. As for testing wise, I got some of the color and details back even with his very small posted jpg as shown below using my project. Other programs can then repair the chroma damage furthur, such as Topaz.
Now obviously, he would want to re-shoot, but if it’s impossible, I’m simply giving him the best way I know how to salvage his problem.

https://technicolorsoftware.hostzi.com/