Also leaving water out causes loss of oxygen in the water and this is not something that's helpful.
So after looking into it I guess it really depends on where in North America you live and there is no standard exactly and can change depending on a number of factors throughout any given year. The compound chloramine occurs after treating chlorinated water with ammonia, so if you have chloramine is in your water you need to treat the chlorine and ammonia. That being said plenty of use of plain chlorine seems to take place and sunlight will work. I guess contact your water company or test your water to know.
As for loss of oxygen you can try a bubble stone.
Or if you're some Mr money bags you can buy a big ass expensive water treatment system lol.
All this aside I still think the reason the op's plant is calcium deficient because the waters calcium content is being filtered.