A few weeks ago I noticed a white flakey substance on the surface of my tub. I have since drained the tub and had to use my power washer and vinegar to clear the flakes. In error, the other day I added too much MA when balancing my water and my PH took a dive. So I have started to add Borax. Problem is the borax does not seem to be dissolving. When the jets are off the borax seems to just sit on the acrylic surface. Its seems to settle in the same places where I had the white flakey stains, which makes me think the Borax was culprit. Is there a certain way to add Borax to the tub? Right now, I simply add borax to a container, add water, stir pretty good, and pour it into the tub. What am I doing wrong?