I just got the SB Stretch a couple weeks ago. I immediately wiped the blade with my tuf-cloth. After using it once as my dinner knife the SB had a patina. I was surprised. I emailed sentry solutions about it the reply said based on my description they thought my tuf-cloth had died. They can only be re-charged (or whatever) with mineral spirits so many times I guess. So, now I'm using a new cloth and am very curious how that will work. This was the first time I had any corrosion of any kind after using tuf-glide or tuf-cloth. I'll find out in about an hour when I eat dinner. Anyway, they included a "test" to see if your tuf-cloth needs replacing or not.
Here is the test.
Based on your description it does sound like your TUF-CLOTH needs to be retired. There is a way to test a TUF-CLOTH; you can do this on the whole TUF-CLOTH but cutting off a little piece will work too, that way you won't compromise the current state of the entire TUF-CLOTH. So the test is basically- with the "moist/wet" TUF-CLOTH wipe a small section of clean, clear glass. After cutting a small section or corner of TUF-CLOTH, allow this cut piece to dry completely. Once it is dry use the small, dry section to wipe a small section of the clean, clear glass next to the section you wiped with the "moist" TUF-CLOTH. Compare the films left on the glass visually; the moist section should look "heavier" than the dry wiped section. If you can wipe off the "moist wiped" section film and the "dry wiped" section easily, that means the active ingredients which were trapped on the fibers of the cloth have been exhausted.
We hope this helps.
PS (for those wondering)
Lots of comments have been made about tuf-cloth's being used on knife blades and then using for food prep. According to Sentry Solutions it boils down to this or this is how I look at it. While tuf-glide has not been approved by the FDA I believe the consensus is that after it dries on a blade and then wiped off or even washed nobody who uses the knife to cut their food will drop dead. So, if I want to use my EDC knife for cutting food, which isn't very often, I go ahead and do it.