For hardwater, I've used Lucas Formula. It's a two part mix, General Hydroponics flora micro and flora bloom, get the "flora micro for hardwater."
Although, I recently decided to try dyna-gro two part veg and flower nutes, using the same hard water, and my girls in veg are doing much better then Lucas Formula or even GH's proper vegging formula even with the micro meant for hardwater. I'm looking forward to seeing how flowering goes with dyna-gro.