What causes towel discoloration

Yeah, if your using that stuff then use white towels, hand towels and facecloths - the stuff doesn't rinse off with just a few splashes of water either and there is always some left around the edges so rinse off thouroughly with a white facecloth to get all traces off.  We've ruined lots of towels too

The spots look like bleach spots to me. Here's my experience and why I say this. I went through a period where I started getting spots like that on clothes. After a long problem solving process and many bleach spot clothes, I came to learn that the bleach dispenser wears out over time. The bleach dispenser is the little plastic cup that you put the bleach into. I got a new one, which looked just like the old one. I changed it out and it solved the problem.