discolored hot water

After I accidentally broke the cold water supply line to my bathroom sink due to corrosion, I was eventually able to learn how to solder copper pipe, and successfully replaced both lines without any leaks! Unfortunately the tap water (both lines) has since taken on a noticeably yellow tint...

I have 80 gal Bradford White HWH, which I use as a holding tank most of the time. I also have a geothermal HWH which is primary source of hot water. When I take the geothermal HWH offline and turn the electric elements on, I get a yellowish color to the hot water. I replaced the elements and...