Greg's experiments have been so well conducted that I have had to modify many of my statements on fixing and washing as the results he got were clear and undeniable.
But, there is one thing common to Greg's data and your process data. That is image stability. Processing in coffee will not change the overall image stability of a B&W image. It is, after all, Silver! However, fixing and washing tests have the disadvantage of changing image stability and this may not be apparent for years. The use of a hypo test kit and a silver test kit will help pinpoint any residual problem.
In color, the change in image stability by using CD-4 instead of CD-3 cannot be tested except by draconian, lengthy and expensive tests. You are introducing this type of problem. In addition, the change in dye hue cannot be easily tested except by the use of a spectrophotometer. Again, this is something that our eyes may not see well in the film or paper print, but does surely degrade (or substantially change) color. So, your experience at "good" pictures might not pass the test of time, nor that of a good eye for color.