What i know for distiled water is that it is pH neutral untill it makes contact with air, and it has nothing in it (we dont even use it for mixing with home made alchohol just becouse of that) and by mixing it ~50/50 i think i lower the hardness by half and still have good stuff, i just dont know if it is chlorine or chloramine thats in it.
Another thing that bothers me is that i store my whater (when i dilute it) in a bottle in dark, but a closed bottle, can this be bad for my plants?
It will lose the dissolved oxygen, put an aquarium air stone in the bottle for a day before you are going to use it, made a dramatic difference in my grow.