On Jun 4, 3:59*pm, "Dimitrios Paskoudniakis"
wrote:
We noticed that most of the plastic fixtures in our hot tub, naturally gray
in color, are all coated in a gold color below the waterline. *My wife
performed a routine chemical treatment yesterday, including adding pH raiser
and Alkalinity raiser. *A chem strip shows normal levels.

Any idea what this is and will it resolve?

Probably you have an excess of iron in your water. Not gold, rust!
The rust appears when the water is exposed to air, heqating speeds the
process.
It may be from the pipewirk but more probably from the source of
water. Ground source water is particularly prone to this, esp.if
there has been mining in the area..

It will be very difficult to completely remove without damaging the
tub.
Prob.weak acid such as vinegar.