The bleach does not require a starter per some resident kodak Photo Engineer.

Do not mix the concentrates. It fizzes violently and gives off noxious fumes. I've tried. They need to be added in the specified order with stirring to the specified amount of water. Although once I swapped the order by accident and it was fine AFAIK.

I use distilled water to mix the developer (sometimes) but always the final rinse/stabilizer. This has eliminated the marks. For non critical work tap water is probably fine for the developer. You can try distilled and tap water and if you notice a difference, then use distilled.