I've had a quick scour of the web and MFT and I can't find much on stress bars. Nothing at all actually. I know that engineer gobys change their stripes from horizontal to vertical as they mature. I am not sure at what age they begin to mature (mine are certianly still juveniles) but I did wonder if these marks might be related to this. My water param's are all spot on, everything reads zero and they have burrowed a nice secluded home under a large peice of dead branch coral, so if they are caused by stress, I cannot see what is causing them. As I said, they do seem to come and go.
On another point, I just want to say how satisfying it is to have sparkling clear water. *BOUNCINGS