Yea, I'm not really worried about the lockout in this thread. I'm really looking for advice on a hard water nute recipe, or how to calculate it.
You are using well water I assume? (I have well water too) by hard do you mean there's a lot of iron in it or bicarbonates (high alkalinity)?
One thing you could try is a liquid humic supplement, I still use fox farm Big Bloom which has an extremely low npk (won't mess with you recipe) and has humic, fulvic and amminos in it which will help naturally chelate iron and other minerals that are in an unavailable form or difficult to assimilate form. Put a capful in your mixing res with your water before you add your nutes.
If your dealing with high alkalinity and can't get RO water you could try ph downing your water to 4.5 and let it sit for 24 hrs, add nutes and ph to your needs.
Btw if you need to up your ph, use a product with potassium hydroxide, the other ingredient used (I can't remember now) can cause nutrient lockout, the higher end nutrients will use the potassium hydroxide, GH uses the other ingredient
I guess this may not answer your question as to how to calculate your recipe but without knowing what the chemical makeup of your water source is you can't really solve/prevent the problem. If it's a well you need to get the water tested or get filtered/RO water which is where I'm headed soon.
Good luck