I feel slightly guilty for my unhelpful post at #5 above.

You do see that more detail is required for anyone to compare what you are doing with what anyone else is doing? For example, it could even be possible that you are carrying out a multiple stage, very complicated, toning and bleaching process with washing and drying at every step - unlikely, but quite possible. The problem is clearly not a very general one (as you have seen yourself over the last ten years, from your post) so something must have changed somewhere....

Giving more information would help you solve the problem, by bouncing ideas off the forum members, and will remain available to help future "googlers" with an apparently similar problem.