Looks like acid staining to me, has the appearance of droplets that have hit the stone, and one of the cobble stones behind it in the 1st pic looks stained also, because you mentioned that you added acid to the pool from the pools edge, and as easy as it is to spill some while doing that, would be what i would want to know happened, not that my stones are going to turn orange over time.
Because that style, and color coping stone works very well with the rest of the color scheme around the pool area ( blue )
I would expect my pool builder to explain to me that if i chose this coping material i would have to understand that the material can bleed an orange color that looks like a stain, and will make your wife cry.
That way i will most likely choose another material that wont do that, because the last thing i would want is to find out my carefully designed pool and blue color coordinated coping stone also doubles as a "mood ring"
If this is a natural effect that the blue stones change color, i wouldn't be happy about it.