I have been frustrated with my recent efforts when thiocarbamide toning ilford multigrade warmtone fb. I am aware of the dangers of too strong a bleach attacking the highlights so have made up a solution of 1:49 to avert this. After immersing the prints in the bleach for only 30 seconds I am still losing my highlights (from about zone 7 up on the grayscale). What am I doing wrong. Is my bleach too strong, or should I reduce the time in the bleach still further? Any help gratefully received.