Sorry I'm horrible with keeping up with threads. I checked a couple of my nymphs. They are younger than yours and they do have markings on each segment, though they are more brown and more well-defined than on the female pictured (aka they don't look like smudges). As for the discoloration on the abdomen tip, something is definitely going on :/ I would suggest keeping her away from the rest of your nymphs just in case it can be spread, as for how to cure it.. I honestly have no idea.
I used to keep T. sinensis for a while and they were delightful in my opinion ^^ They were one of the only species I've ever witnessed do a backflip and they would jump up from hand to hand as I made a ladder with my hands in mid-air for them! The only reason I stopped breeding them is because they are so widely available already.