White water stains in new dark plaster pool

We just filled a new construction plaster pool, while it was filling the children got loose :) and played with hose. I now have a ring in the shallow end of the pool where the plaster got wet then dried. The pool company told me that scale-tec and daily brushing will resolve the issue but it has been several days and I see no difference. Any advice?

The pool is 18,500 gal, 64fl of scale-tec was added after the fill was complete. Acid is being added daily to keep PH in check.